dot net interview questions and answers

.Net Remoting IQ-PART-1

2010-02-08T22:19:00.000-08:00

Define windows process

Answer - A process is an instance of a running application.
Each process is allocated its own block of available RAM space.
No process can access another process code or data.
If the process crashes, it dies alone without taking the entire OS or a bunch of other applications down.

Define channels in .NET Remoting

Answer - Channels represent the objects that transfer the other serialized objects from one application domain to another and from one computer to another, as well as one process to another on the same box.
A channel must exist before an object can be transferred.

What security means available for .NET Remoting in System.Runtime.Remoting?

Answer - None. Security should be taken care of at the application level.
Cryptography and other security techniques can be applied at application or server level.

What is a formatter in .Net Remoting?

Answer - A formatter is an object that is responsible for encoding and serializing data into messages on one end, and deserializing and decoding messages into data on the other end.

.NET Remoting and Web services.

Answer - Use remoting for more efficient exchange of information when you control both ends of the application.
Use Web services for open-protocol-based information exchange when you are just a client or a server with the other end belonging to someone else.

Name the distributed systems available apart from .Net Remoting.

Answer - Distributed Computing Environment/Remote Procedure Calls (DEC/RPC),
Microsoft Distributed Component Object Model (DCOM),
Common Object Request Broker Architecture (CORBA), and
Java Remote Method Invocation (RMI).

How do you implement distributed applications in .NET?

Answer - .NET Remoting and ASP.NET Web Services.
Classes for the same are in System.Runtime.Remoting and System.Web.Services.

Define proxy in .NET Remoting.

Answer - Its a fake copy of the server object that resides on the client side and behaves as if it was the server.
It handles the communication between real server object and the client object.
This process is also known as marshaling.

Define remotable objects in .NET Remoting.

Answer - Remotable objects are the objects that can be marshaled across the application domains.
You can marshal by value, where a copy of the object is created and then passed to the receiver.
You can also marshal by reference, where just a reference to an existing object is passed.

Define SingleCall activation mode in .Net Remoting.

Answer - If the server object is instantiated for responding to just one single request, the request should be made in SingleCall mode.

Define Singleton activation mode in .Net Remoting.

Answer - A single object is instantiated regardless of the number of clients accessing it.
Lifetime of this object is determined by lifetime lease.

Define the lease of the object.

Answer - By implementing ILease interface when writing the class code.

.NET Remoting versus Distributed COM

.NET Remoting is the successor of DCOM. Microsoft DCOM is a solution for distributed object and very good in terms of performance when components are in the same network. But its drawbacks in the internet connected world are visible. It uses proprietary binary protocol which is not supported by other object models, thus can't support interoperability across platform.
.NET Remoting uses TCP or HTTP protocol that is supported by most of the object models. This allows .NET Remoting to be adaptable to the network environment in which it is being used.

Advantage of Remoting over Web Services

Answer - .NET Remoting allows objects to interact that can be hosted in different application domain within the same process or different process. The objects can also interact over intranet or internet. It supports many different protocols unlike Web Services that works over SOAP/HTTP protocol. .Net Remoting can work on TCP protocol that provides speed benefit from its counterpart.
Being tied up with IIS, .Net Web service can only work with producer /consumer model whereas .Net Remoting can share objects from any type of application. .Net Remoting being part of .Net Framework support full .Net type system and can expose any object to the client. .Net Web Service supports on those types that can be expressed with XSD.

When should we choose .Net Remoting over .Net Web Services?

Answer - .Net Remoting provides distributed solution for a corporate use. So, if you need distributed environment to be implemented for internal use, .Net remoting is the best choice.

If you require a faster distributed solution, .Net Remoting with TCP protocal using binary format is faster than Web services. .Net Remoting is better solution when large transfer of data is required. Web Services provide an open-protocol-based exchange of information. Web Services are best when you need to communicate with an external organization or non .NET technology.

What are the ways to configure Remoting objects before client can use them?

Answer - There are two ways that the remoting objects can be configured. They can be configured by calling configuration methods inside the application. .Net Framework allows configuring objects also by adding configuration section in the application configuration file or machine.config file. Application-level XML settings take precedence over machine.config. When you apply any change in the configuration section, you don’t need to recompile the code. On the other hand, any change in the setting applied programmatically would require recompiling the code.

Define Delegates.

Answer - A delegate acts like a strongly type function pointer. Delegates can invoke the methods that they reference without making explicit calls to those methods. It is type safe since it holds reference of only those methods that match its signature. Unlike other classes, the delegate class has a signature. Delegates are used to implement event programming model in .NET application. Delegates enable the methods that listen for an event, to be abstract.

Define Events.

Answer - Events are one of the members of the class. When any noteworthy activity occurs in the application, an event is raised which sends out the message to the other part of the application which handles the event. The event can carry arguments that contain information about the event. The method which handles the event must have the same signature as the event itself. Events are commonly used in the applications with graphical user interface elements such as buttons, textbox etc. An event is triggered when any action such as mouse click occurred in the interface element. The event-based programming model can be used in the non-GUI applications such as .NET Remoting application. An event in remoting.net occurs when the state of the application changes.

.Net Remoting IQ-PART-2

2010-02-08T22:17:00.003-08:00

What is asynchronous programming?

Answer - .Net Remoting supports asynchronous programming. In this model, a call is made to a class method while the calling program continues to execute. This increase application speed as the application continues to execute without waiting for the called methods to finish execution.

When do we use delegates in your remoting applications?

Answer - You use delegates to implement callback functions, event programming, and asynchronous programming in your remoting applications. Events use delegates to enable callback functions to the client in remoting applications.

What are the ways to renew lifetime leases of objects?

Answer - A client can renew the lifetime lease of an object by calling the ILease.Renew method.

What are the types of remotable objects?

Answer - The two types of remotable objects are

Marshal-by-value objects - These objects are copied and passed by value out of the application domain. When client calls a method on marshal-by-value-object, the remoting system creates a copy of this object and passes the copy to the client application domain. The copy hence received can handle any method call in client domain. Using Marshal-by-value-object reduces resource consuming trip across network.

Marshal-by-reference objects - The clients that use these objects need a proxy to access the object remotely. When client calls a method on Marshal by reference object, the remoting system create proxy object in the caller application that contains the reference of all method and properties of the object.

What are the Security features in .Net Remoting.

Answer - .Net Remoting is integral part of .Net Framework, so it has access to all security features of Framework. If remoting objects are hosted using IIS, it leverages the entire authentication and authorization features that are available to Web based protocols. If hosted other than HTTP protocols over IIS, then you have the opportunity to create your own security infrastructure.

What are the information required to configure remote objects?

Answer - Following information to be provide to configure remote object.

Activation type for the remote object
Channels
URL of the remote object
Type metadata of the remote object

Explain Serialization Formatters in .NET Remoting.

Answer - In .Net Remoting, the objects are shared over distributed network. The objects are transmitted in serialized form. The objects are first serialized into message data before it is sent with the wire. On the other end of the wire, this serialized data is read and desterilized back to the actual object. This process of converting objects into message data is done by serialization formatters. .Net Remoting supports two formatters.
SOAP Formatter
Binary Formatter
SOAP Formatter converts objects into XML string whereas Binary Formatter converts an object's state into a binary stream. The binary serialization formatter is slightly faster.

What are the requirements to enable remote components to interact each other?

Answer - To enable communication between objects across remoting boundaries, you need to have
A server object to expose service
A client that calls server object to consume service
A message transmission protocol

Steps to publish an object outside the service domain.

Answer - To publish a service outside the service domain, you need to:

Identify the application domain that will host the service.
Identify the activation model: server activation or client activation.
Identify and create a channel and a port.
Identify how the client application obtains the metadata information about the service.

Define Client Activated Objects (CAO).

Answer - Client-activated objects are objects whose lifetimes are controlled by the client, i.e. calling application domain. This mode works in similar fashion to the model where object is local to the client and referenced object's lifetime is controlled by the calling object. When instance of server object is created, object reference is obtained in the form of proxy.

In COM model, clients hold an object in memory by holding a reference to it. The object is released from the memory when the entire client releases the reference. But in .Net Remoting, client-activated objects use lifetime leases to determine how long they should continue to exist. When a client creates a remote object, it can specify a default length of time that the object should exist. If the remote object reaches its default lifetime limit, it contacts the client to ask whether it should continue to exist, and if so, for how much longer. If the client is not currently available, a default time is also specified for how long the server object should wait while trying to contact the client before marking itself for garbage collection. The client might even request an indefinite default lifetime. Client-activated instances serve only the client and the reference that was responsible for their creation.

To create an instance of a client-activated type, clients either configure their application programmatically or using a configuration file and call new, or they pass the remote object's configuration in a call to Activator.CreateInstance.

Explain Marshalling and its types in .Net Remoting.

Answer - Objects can't be transmitted as such over communication channel. The objects are packed into message buffer before transmitted. This process is called marshalling. There are two different ways to Marshal objects

Marshal by Value: Server creates copy of the remoting object's state and passes it to the client. You need to implement your classes to have marshal by value features either by implementing ISerializable interface or using attribute. Here you need to copy whole object to the client which means with large size object, the communication overhead is significant.

Marshal by Reference: In this type proxy is created by the reference of the server objects. Class must extend the System.MarshalByRefObject to implement marshal by reference. Here, client keeps server object reference which means round trip to server with each method call.

Summary of .Net Remoting

.Net enables interaction between applications over distributed network.

To develop a Remoting application, you need to create client and server objects. You need to activate the objects and use reference of the server objects in client to communicate.

Channels allow application to send and receive messages using protocal like TCP or HTTP.

You can use delegates in Remoting application to implement event based programming and asynchronous programming.

Asynchronous programming in Remoting application helps to calls remote methods while client continues to execute other local method.

To host remote object, server needs some information about the objects.

The information can be provided programmatically in the code or can be loaded from configuration section of application configuration file or machine.config file.

Being part of .Net Framework, .Net Remoting can implement role based security. Moreover, it can leverage all security features of ASP.NET, if it hosted in ASP.NET.

What is .Net Remoting?

.Net Remoting enables communication between applications across separate domains or networks. .Net objects are exposed to remote processes to have interprocess communication. With remoting, we can use TCP or HTTP communications protocols on any port. We can use text or binary formatting. .Net Remoting supports server activated (single call and singleton) as well as client activated objects.

Describe the .Net Remoting Architecture.

.Net Remoing allows communication between server and client objects. To facilitate this, when new instance of remote object is created in the client application, the client receives reference (called proxy) to the server object. This proxy object contains references to all the methods and properties of the server object. When the client object calls any method (the call actually on proxy object), which resolves the references and invokes server object, receives the result and pass on to the client application.

What are the remotable and non-remotable objects in .Net Remoting.

The remotable objects are the objects which can be distributed accross domains, can be used with domain. The non-remotable objects are the objects which can't be distributed accross domains. In distributed system, if an object is very big, we can make it non-remotable object.

Describe the type of remotable objects in .Net Remoting.

Marshal-by-value-objects - When client calls a method on marshal-by-value-object, the remoting system creates a copy of this object and passes the copy to the client application domain. The copy hence received can handle any method call in client domain. Using Marshal-by-value-object reduces resource consuming trip across network.
Marshal-by-reference-object - When client calls a method on Marshal by reference object, the remoting system create proxy object in the caller application that contains the reference of all method and properties of the object.

What is the difference between XML Web Services using ASMX and .NET Remoting using SOAP?

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XML Web services are more restricted than objects exposed over .NET Remoting.
XML Web services support open standards that target cross-platform use.
XML Web services are generally easier to create and due to the restricted nature of XML Web services, the design issues are simplified.
XML Web services support only SOAP message formatting, which uses larger XML text messages.
Communication with .NET Remoting can be faster than XML Web service communication with a binary formatter.
XML Web services are designed for use between companies and organizations.
XML Web services don't require a dedicated hosting program because they are always hosted by ASP.NET.
Consumers can use XML Web services just as easily as they can download HTML pages from the Internet. Thus there's no need for an administrator to open additional ports on a firewall as they work through MS-IIS and ASP.NE

Remoting.Net vs Web Services

2010-02-08T22:17:00.001-08:00

Both .Net Web services and .Net Remoting are Microsoft solutions for distributed application. Before choosing one of them for application development, let’s identify the differences between these technologies.

Protocol
.Net web services can be accessed only over HTTP whereas .Net remoting can be accessed over any protocol including TCP, HTTP, or SMTP.

Performance
In terms of performance, .Net remoting is faster than its counterpart web service when it uses TCP channel with binary formatter. But if you use soap formatter in .net remoting, web services with soap formatter either with TCP or HTTP channel provides faster solution.

Security
.NET Remoting can be hosted either in IIS or in other container. If hosted in IIS, .NET Remoting can benefit all security advantages of IIS. But when hosted other than IIS, the application has to take care security aspect itself.
On the other hand, .Net web services are hosted in IIS, by default. So, it leverages all features of security provided by IIS.

State Management
Web services are a stateless in nature like web application. You need to use state mechanism to retain state. You can use session or application object to maintain state. In .Net Remoting, Singleton objects can share state whereas if you don’t need to maintain state, you can use Singlecall objects.

Interoperability
Web services support heterogeneous environments which means client and remote object can be built in any platform.
.NET remoting requires the client be built using .NET, enforcing homogenous environment.

Reliability
Since .Net web services are hosted using IIS, they are reliable whereas .Net remoting application needs to maintain security on its own if not hosted using IIS. When hosted in IIS, .Net remoting is also as reliable as web services.

Ease of development
Create and consuming .Net web services are easier process. To create remoting object, you need create remote object, hosting application to host remoting object and configuration file to specify type of channel and formatter to be used by remoting object.

Asynchronous Programming in remoting Application

2010-02-08T22:16:00.002-08:00

.Net Remoting supports asynchronous programming. In this model, a call is made to a class method while the calling program continues to execute. This increases application speed as the application continues to execute without waiting for the called methods to finish execution.

Asynchronous Programming in remoting Application

There are two ways that the remoting objects can be configured. They can be configured by calling configuration methods inside the application. .Net Framework allows configuring objects also by adding configuration section in the application configuration file.
When you apply any change in the configuration section, you don’t need to recompile the code. On the other hand, any change in the setting applied programmatically would require recompiling the code.

Remoting system requires certain information about remote objects to be hosted which are as follows

Activation type
Channels
URL of the remote object
Type metadata

.Net Framework provides RemotingConfiguration class in the System.Runtime.Remoting namespace that allows configuring object programmatically.

In .Net, you can have configuration setting in the application configuration file or in the machine.config file. You can use RemotingConfiguration.Configure method to load the setting in the code, e.g.

RemotingConfiguration.Configure("AppConfig.exe.config")

The configuration attributes in the XML configuration file of the application are below.

This element contains the information about the remote objects.

This element contains the remote object.

This element has three attribute such as mode, type, and objectUri. Mode can be Singleton or SingleCall. Type is the name of the assembly that contains type implementation. ObjectUri specifies the endpoint for the URI of an object.

This element contains information about the client-activated objects that are exposed by the application.

Events and Delegates in Remoting Applications

2010-02-08T22:16:00.001-08:00

Events are one of the members of the class. When any noteworthy activity occurs in the application, an event is raised which sends out the message to the other part of the application which handles the event. The event can carry arguments that contain information about the event. The method which handles the event must have the same signature as the event itself. Events are commonly used in the applications with graphical user interface elements such as buttons, textbox etc. An event is triggered when any action such as mouse click occurred in the interface element. The event-based programming model can be used in the non-GUI applications such as .NET Remoting application. An event in remoting.net occurs when the state of the application changes.

A delegate acts like a strongly type function pointer. Delegates can invoke the methods that they reference without making explicit calls to those methods. It is type safe since it holds reference of only those methods that match its signature. Unlike other classes, the delegate class has a signature. Delegates are used to implement event programming model in .NET application. Delegates enable the methods that listen for an event, to be abstract.

Steps to implement delegate to listen for events in the remoting application

Define a delegate that wraps an event handler method to handle the event.
Implement a class that raises the event.
Implement class that handles the event

.Net Remoting Channels

2010-02-08T22:15:00.001-08:00

Channels are the objects that remote objects use to communicate with each other. It allows applications to send and receive messages using protocols such as TCP and HTTP. It is a message carrier that converts the message in either as XML or binary format before sending message across boundary.

In .Net Framework, channel's classes and interfaces are included in System.Runtime.Remotig.Channels namespace. A channel needs to be registered to the remoting system infrastructure both at client and server side before it receives or send data.

Based on the protocol used by the channel, you have
HTTPChannel
TCPChannel

HTTPChannel

.Net Framework provides System.Runtime.Remoting.Channels.http namespace that provides classes to use HTTPChannel. You can use HTTPChannel when interoperability is the main issue. HTTPChannel uses SOAPformatter to serialize messages into XML format before sending messages.

TCPChannel

.Net Framework provides System.Runtime.Remoting.Channels.tcp namespace that provides classes to use TCPChannel. This kind of channel is used when performance is main issue. TCPChannel uses BinaryFormatter to serialize messages into binary stream before sending messages.

.Net Remoting Overview

2010-02-08T22:13:00.000-08:00

Distributed application is a set of components distributed across network and work as if all the components are there on the same computer. These components based technologies can be developed using DCOM, CORBA, RMI etc. These technologies are good for intranet environment.

Microsoft has provided suitable framework for developing distributed application through .Net Remoting and Web Services. Remoting.net allows components to interact across application domains, processes, and machine boundaries. It enables your applications to take advantage of remote resources in a networked environment.

Web Services are best suited when clients outside the firewall calling components on the server over the Internet.

Remoting.Net is the best solution when clients and components are inside the firewall. It requires the client to be built using .NET which means it can’t work in heterogeneous environments.

.Net Remoting uses channels (HTTP and TCP channels) to transport messages to and from remotable objects. The HTTP channel uses the SOAP protocol to transport messages which means all messages are serialized to XML. The TCP channel uses a binary stream to transport the messages.

.Net Remoting supports two activation modes: Singleton and SingleCall. Singleton mode allows only one instance of an object at any time which means all requests are serviced by the single instance. You can maintain state across each request using this mode. SingleCall Mode creates a new instance of the object for each client request and are stateless.

.NET Remoting when hosted with IIS, can use all the security features of ASP.NET. But you need to implement your own security features for the application if channel is hosted in the process other than aspnet_wp.exe.

What is .Net Remoting?

2010-02-08T22:12:00.000-08:00

Describe the .Net Remoting Architecture.

What are the remotable and non-remotable objects in .Net Remoting.

Describe the type of remotable objects in .Net Remoting.

What are the types of activation modes in .Net remoting?

Server Activation Mode: In this mode, objects are created on the server when we call a method in the server class and not when we create instance using new. In this type of scenario, the client is always connected with server but the services are activated only when we call the method of the server class. We can create server activated object as a Singleton or SingleCall object. If we create server object as singleton, a single instance will manage all the clients. If we create server object as singlecall, the remoting system creates object each time a client method invokes a remote object.

Client Activation Mode: This object gets created when we create instance using new keyword. In this mode, client application domain defines the lifetimes of client activated objects. The client domain defines the lifetimes of client-activated objects. They use lifetime leases to determine the duration of their existence and after the lifetime expires, the object is marked for GC.

Describe the term Channel in .Net Remoting.

In .Net Remoting, an application use Channel to send message to another application which is runing in different domain or process. Before sending message, Channel converts message into appropriate format like XML or binary format. The channel that carries message(Mashalled parameter) can use protocal like TCP and HTTP. Channel can be HTTPChannel and TCPChannel. The HTTPChannel use soapFormatter to serialize messages into the XML format using SOAP protocal. Using SOAP method allows the client to call method on the remote object that might not be using .Net framework. The TCPChannel use binaryFormatter to serialize message into binary stream.

DCOM vs .Net Remoting

2010-02-08T22:11:00.000-08:00

Answer - .Net Remoting is the successor of Distributed component object Model(DCOM). Both these technology are introduced by Microsoft that enable inter-process communication across application domains. DCOM was very successful technology. But it is never treated as best technology for inter-process communication because of lack of its support for interoperability across platform.

.Net Remoting is a new technology that ship with .Net Framework. It has all those features which are missing in DCOM. There are other pain involve with DCOM such as difficult to control format or channels, message trace is painful, change in configuration setting such as channels or port is not easy. DCOM is hard to learn and complicated to deploy and to maintain.

Differences between these two technologies are as follows.

DCOM technology is based on the COM architecture whereas .NET Remoting is primarily based on .NET Frameworks.

DCOM is based on proprietary binary protocol which is not supported by all object model, thus has big drawbacks in the internet world.

DCOM is based on RPC protocol whereas .Net Remoting can use TCP or HTTP protocol which is stardard protocal in the market.

DCOM is not firewall friendly, can't choose port. .Net Remoting, on the other hand, works easily across firewalls.

.Net Remoting supports cross platform communication which is not possible with DCOM (only for windows platform).

Components created DCOM involves complex deployment in windows registries whereas .Net Remoting involves easy deployment using either xml based configuration file or programmatically in the code.

DCOM uses windows security features whereas .Net Remoting can use security features of IIS if hosted with ASP.NET. .Net Remoting, if hosted other than ASP worker process, allows to create own security mechanism for the application.

In DCOM, server is started by Service Control Manager (SCM) upon receiving the activation request from the client whereas in .Net Remoting, IIS is responsible to start server service. If not hosted with IIS then client request will fail if the Remoting server is not already started.

DCOM manages remote object lifetime by frequent pinging of clients whereas .Net Remoting has more efficient leasing mechanisms to maintain object lifetime.

Define windows process

Advantages of .Net Web Services

2010-02-08T22:10:00.001-08:00

Web Services are supported on a wide range of platforms.

Web services may extend its interface and add new methods without affecting the clients as long as they still provide the old methods and parameters.

A client makes a request to a web service, the web service returns the result, and the connection is closed. There is no permanent connection. This makes it easy to scale up and support many clients at a time.
Firewalls can pose a challenge for distributed object technologies. The only thing that almost always gets through firewalls is HTTP traffic on ports 80 and 443. Because web services use HTTP, they can pass through firewalls without explicit configuration.

Explain in brief Web Service Standards.

Following are the standards used by web services:

WSDL
WSDL is used to create interface definition for a web services. It describes all about methods to the client, i.e. methods available in a web service, their parameters and return values.

SOAP

SOAP, Simple Object Access Protocol is a communication protocol, a way to structure data, based on XML. The web services use SOAP message format to encode information before sending.

HTTP
The SOAP message format in web services uses HTTP as communication protocol, i.e. SOAP messages are sent over HTTP channels.

DISCO
It is used to create discovery documents that provide links to multiple web service endpoints. The DISCO standard creates a single file that groups a list of related web services. A company can publish a DISCO file on its server that contains links to all the web services it provides.

UDDI
A standard for creating business registries that catalog companies, the web services they provide, and the corresponding URLs for their WSDL contracts.

Define the specifications that help in the discovery of a web service.

DISCO

DISCO, an abbreviation of discovery, is a file that groups together a list of related web services. A company that offers web services publishes a DISCO file on its server that has links of all the web services it provides. The client requests this file to see all the available web services. This standard is useful when client already know about a company that offers web services. You can also use DISCO standard while working in local network. It is not helpful to find all web services over the internet.

UDDI

UDDI (Universal Description, Discovery, and Integration) offers centralized directory for web services over the internet. It hosts web services from different companies and can be used by the clients to find web services of their specific need. To make web services shared publicly, they have to be published in UDDI.

What are the data types supported by Web Services?

.Net web services are built on XML-based standards for exchanging data. This means .NET web services can support only those data types that can be recognized by the XML schema standard. There are many proprietary .Net objects such as FileSteam, Eventlog etc. are not supported in the web services. These data types are .Net specific types that are not universally recognized, i.e. .Net specific only.

You can even exchange custom objects using .Net web services. The only limitation is that only public data members are transmitted, and all public members and properties must use one of the other supported data types.

You can use DataSet and DataTable to return information from database but can't use other ADO.NET objects such as DataColumns and DataRows.

.Net offers a distributed technology called .Net remoting that can plays around wide range of .Net specific data type. But unfortunately, .Net remoting doesn't support client other than .Net.

Testing and consuming a .Net web service.

Testing a Web Service

.NET has a test web page that ASP.NET uses automatically when you request the URL of an .asmx file in a browser. This page uses reflection to read and show information about the web services, such as the names of the methods it provides.

Consuming a Web Service

Web services are built on XML standard. So, a client needs to equip itself to understand XML-based message in order to exchange messages. The .Net framework provides proxy component that enable clients to interact with web services. The proxy has all necessary information that can be utilized by the client application to share data with web services.

The proxy class wraps the calls to the web service's methods. It generates SOAP message format and manages the transmission of the messages over the network (using HTTP). When it receives the response message, it converts the results back to the corresponding .NET data types.

You can create a proxy class in .NET in two ways:

By using wsdl.exe command-line tool
By using Visual Studio web reference feature

Why do we need .Net Web Services?

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We have a number of heterogeneous technologies available on internet. The demand for reusable components across platforms and programming languages are high. Most of the components have the limitation that they can't share or exchange data across different platforms, they are mostly language specific or platform specific. The technologies like COM, RMI, CORBA etc. contributed best to fulfill requirements to some extent, but components result from these said technologies are mostly either language specific or platform specific.

To avoid above problem, we need to have web services. Through web services we have overcome the problem of interoperability between languages and platforms. Web services uses SOAP as transport protocol which uses a text based messaging model, i.e. XML to communicate between disparate systems.

Deploying a Web Service

Deploying the .Net Web Services is as simple as any ASP.NET application. Similar to ASP.NET applications, you need to copy or upload the .ASMX file and the .DISCO files to the appropriate directories, and that's it.

Explain in brief different distributed technologies.

The need of distributed technologies arises with the requirement of distributed computing applications. The distributed computing allows partitioning of application logic into units and spreading the unit over different computers of a network or across different networks. This helps in spreading out loads over many computers. The components once developed can be reuse by other applications. There are many technologies developed to allow the distribution and reuse of application logic.

Advantages of the distributed components:

The key benefit of having distributed components is that they spread out the load over different machines.
The components can be upgraded without disturbing the clients' code.
The distributed application improves security. For example, a company who has many agents wouldn’t like those agents to have direct access to its database. Instead, these agents can be granted access to the components running on the corporate server which can be controlled and restricted.

Web services vs. CORBA and DCOM.

Web services
Web services use HTTP protocol for sending and receiving messages between the applications.
The data encoding in web services is based on XML.
Web services are defined using WSDL (Web Services Description Language).

Web services are discovered using UDDI (Universal Description, Discovery and Integration).
Web services are firewalls friendly.
Web services supports interoperability i.e. cross platform integration is possible.

CORBA and DCOM

These technologies use non-standard protocol, i.e. CORBA uses IIOP (Inter Internet Object Protocol), and DCOM uses RPC (Remote Procedure Calls)
CORBA components are defined using CORBA Interface Description Language; DCOM components are defined using Microsoft Interface definition languages
CORBA components are discovered using the CORBA registry, DCOM using the Registry.
DCOM is a proprietary protocol that does not support interoperability and has firewall problems as DCOM transfers data in binary format and it uses many ports to call remote functions.
CORBA uses the IIOP protocol, which is non-Internet friendly.
CORBA and DCOM are fine for building enterprise applications that runs on the same platform and not good enough for applications that span platforms and languages.

When to use .Net Remoting over Web services

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.Net Remoting provides distributed solution for a corporate use. So, if you need distributed environment to be implemented for internal use, .Net remoting is the best choice. If you require a faster distributed solution, .Net Remoting with TCP protocal using binary format is faster than Web services. .Net Remoting is better solution when large transfer of data is required.

How does .Net Remoting works?

Remoting.Net allows components to interact across application domains, processes, and machine boundaries, thus allows applications to access remote resources in a networked environment. The interaction of components is made possible through proxy in remoting architecture. When a client calls the remote method, it’s the proxy that receives the call. The proxy then encodes the message using formatter. The messages are then sent over the channel to the server process where listening channel receives the call and passes it to the remoting system. The requested method is then invoked and results are returned back to the client.

.Net Remoting provides an infrastructure where objects of different AppDomains can interact. A client interacts with server object using .Net Remoting architecture. An object interacts with other objects outside AppDomains using proxy since the objects can't access directly anything outside AppDomain.

Point to be noted.
A remote object is implemented by inheriting MarshalByRefObject class.
A client has to obtain proxy activating a remote object by calling CreateInstance, GetObject, or new.
Local objects can be passed as parameters when making remote calls. Local objects are passed by value in a remote call.
The object passed as parameter in a remote call must be serialized.

Activation Model
You need to activate remote object before use. There are two activation modes in .Net Remoting
Server Activation
In this mode, objects are created automatically when a client attempts to access the object. The object doesn't get created when you use new keyword to create instance of the server class.
Client Activation
In this mode, objects are created when you use new keyword to create instance of the server class.

A server object is created and deployed on the network that serves client requests. The server objects have to be registered with the CLR before it can be accessed by client. The details that have to be provided to the CLR are

Name of the assembly that should be loaded to activate the object
The namespace and type name of the object
The name of the endpoint where the object can be accessed
The channels to be used by client to communicate have to be registered.
The registered channels then start listening for clients to connect.

Once a remote object has been deployed, clients can connect and invoke methods on the server object.

In order to access remote object, the client first activates the object by calling new, GetObject, or CreateInstance. On activation request, a proxy is created to represent the remote object. The client message in the serialized form is transported to the server. The type of serialization depends on the channel. For example, when the HTTP channel is used, all messages are serialized to XML and transported over SOAP. On the other hand, TCP uses binary serialization.

On the server side, the requested method is then invoked and results are packaged in a message and returned back by to the client. If the target object is of type SingleCall, it will automatically be garbage collected after the call completes.

Approaches to access server objects in Remoting.Net

First one to have copy of server object on the client machine and accessing local copy of object to call method. This method is good suited when the object is not very big not having too many methods. Copying big object is wastage of client resources which includes network resources and processing time.

The second approach is to create a proxy object that returns reference of all the methods and properties of server object in the client domain. The proxy acts as local object, fake server object on the client machine. Any method call from the client will be served by proxy which in turn access server domain to get response from server object. This approach is good when the object is big with many methods.

Remotable and Nonremotable objects

You have two categories of objects in distributed applications: Remotable and Nonremotable objects.

Nonremotable object can’t be accessed outside its own application domain. This kind of object doesn't allow its methods or properties to be used by remoting system. Remotable objects can be accessed outside its own application domain. The remoting system can use methods and properties of this kind of object.

There are two types of remotable objects

Marshal-by-value-objects - When client calls a method on marshal-by-value-object, the remoting system creates a copy of this object and passes the copy to the client application domain. The copy hence received can handle any method call in client domain. Using Marshal-by-value-object reduces resource consuming trip across network.

Marshal-by-reference-object - When client calls a method on Marshal by reference object, the remoting system create proxy object in the caller application that contains the reference of all method and properties of the object.

Explain the protocols a .Net Web Service uses.

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In .Net, a web service is bind with three different protocols such as HTTP/POST, HTTP/GET, and SOAP. This allows client with three options to choose for communication. The protocols are included in the WSDL file that is automatically generated in .NET.

Http-Get and Http-Post can only be used when name/value pairs of data is dealt with. But when data is complex in nature such as ASP.NET dataset, XML notes etc, then we can use SOAP that serializes data in simpler form before sending.

Explain how to document web services.

ASP.NET web services are considered as self documenting as they provides all information about what methods are available and what parameters they require using XML based standard called WSDL. We can also provide addition information about the web services using their WebService and WebMethod attributes.

You can add descriptions to each method through the Description property of the WebMethod attribute and to the entire web service as a whole using the Description property of the WebService attribute. You can also apply a descriptive name to the web service using the Name property of the WebService attribute. The attributes have name, description and namespace as properties which are shown in following example:

[WebService(Name = "Customer Service", Description = "Retrieve the Customer details",Namespace=http://www.apress.com/ProASP.NET/)]
public class Customer : System.Web.Services.WebService
{
[WebMethod(Description = "Returns Customer Count")]
public int GetCustomerCount()
{ ... }

[WebMethod(Description = "Returns the list of Customer")]
public DataSet GetCustomer()
{ ... }
}

Namespace allows your web service to be uniquely identified. By default, ASP.NET web services use the default XML namespace http://tempuri.org/, which is suitable only for testing. XML namespace simply identifies your web service. XML namespaces usually look like URLs. However, they don't need to correspond to a valid Internet location.

Explain when do we required ASP.NET web services.

ASP.NET web services are the great way to expose your middle tier components via internet. These components offer no issue communicating across firewalls as they use SOAP as transport protocols that transmit structured data using HTTP channel. Thus, message can be easily exchanged through port 80, i.e. through internet data port without being getting hampered by corporate firewalls or proxy server.

Web services can fit in the situation when we require integrating disparate systems written by separate vendors via internet.

Web services are primarily being used for B2B integration like authorizing employees, supplier, electronically signing of invoice etc.

What is .Net Web Service?

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Web service is the way to publish application's function on web that can be accessible to the rest of the world.
Web services are the components that can be used by other applications
ASP.NET offers easy way to develop web services, just precede the functions with a special WebMethod ()> attribute in order them to work as Web Service.
Web services are discovered using UDDI directory services.
Web services are built on XML standard and use SOAP protocol that allows them to communicate across different platforms and programming languages.
Web services easily manage to work across corporate firewalls as they use HTTP protocol which is firewall friendly.
Web services platform elements are
SOAP (Simple Object Access Protocol)
UDDI (Universal Description, Discovery and Integration)
WSDL (Web Services Description Language)
The web services are built on internet standards that are not platform or language specific.
The .Net framework provides in-built classes to build and consume web services.
The components offered by web services are reusable.
The examples of web service components can be shipment tracking, translation utility, weather forecasting, sports scores etc.

.NET web service

What is SOAP?

SOAP, Simple Object Access Protocol is a communication protocol, a way to structure data before transmitting it, is based on XML standard. It is developed to allow communication between applications of different platforms and programming languages via internet.

It can use range of protocols such as HTTP, FTP, SMTP, Post office protocal 3(POP3) to carry documents.

Http-Get, Http-Post works with name/value pair which means transferring complex object is not possible with these protocols, whereas SOAP serializes complex structure, such as ASP.NET DataSets, complex arrays, custom types and XML nodes before transmitting and thus allows exchange of complex objects between applications.

Two components can easily communicate using Remote Procedure Calls protocol. But because of their compatibility and security issues, most of firewalls and proxy server block this type of messages. SOAP uses HTTP channel to transport which makes it widely accepted protocal over the internet.

What is WSDL?

WSDL stands for Web Ser
vices Description Language, an XML-based language that describes Web services and how to access and locate them.

What is UDDI?

UDDI stands for Universal Description, Discovery and Integration. It is an open, Internet-based specification that offers directory service for storing information about web services

Who Benefits from AJAX?

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AJAX offers benefits to both end users and developers. For end users, it reduces the “rich or reach” conflict; for developers, it helps in overcoming the constraints raised by HTTP.

Why End Users Want AJAX Applications

Users tend to view desktop applications as a sort of commitment. They install a program, usually from a disk pulled from a costly shrink-wrapped box. The program consumes hard disk space as well as a position in the program menu. The user may need to update the program periodically or perform an upgrade later on to get new features. If the program is proactive about updating itself, the user is confronted regularly with dialogs about accepting patches or downloads. In exchange for this investment of time, money, and energy, the user gets repaid by an application that is able to leverage the operating system and machine resources. It is a rich application. It has local storage capabilities, offers quick response times, and can present a compelling and intuitive graphical user interface.

More and more applications are accessible from the web browser, where the full resources of the hardware and OS are not available, but the user commitment of a desktop application is not required. Over the years, interacting with a web application has meant a predictable pattern for users. They click a link in the page and the browser flashes while the user waits until the screen is repainted (the dreaded post back). This cycle is repeated again and again. The user looks at what is presented on the page, interacts with it, and clicks somewhere. The browser produces an audible click for feedback and begins to post back to the server. The screen of the web browser flashes blank and some icon spins or flashes while the user waits for a new version of the page to be returned from the server. Many times, the new version of the page is almost exactly the same as the previous version, with only part of the page being updated. And then the cycle begins all over again. This has a sluggish feeling even when the user has a highspeed network connection.

The AJAX set of technologies has changed what users expect from web applications. JavaScript code running in the browser works to exchange data with the web server asynchronously. There is no click sound and the browser does not flash. The request to the server is nonblocking, which means the user is able to continue viewing the page and interacting with it. The script gets the updated data from the server and modifies the page dynamically using the DHTML coding methodology. The user is able to continue looking at the page while parts of it are updated in the background. AJAX is used to provide a more responsive experience, making web applications behave more like desktop installations. JavaScript is used to provide a richer experience with support for drag-and-drop, modal dialogs, and seemingly instantaneous updates to various parts of the page based on user inputs.

A big part of successfully leveraging AJAX technologies is in the perceived performance increase. Users appreciate web applications that anticipate their actions. If you also use JavaScript code in the background to pre-fetch images and data that may be needed, users can get a speedy response without the usual pause that accompanies their actions. Nobody wants to wait for data exchanges between client and server; studies have shown that a time lag between user input and subsequent UI changes can significantly reduce their productivity and give them the frustrating feeling that they are fighting the application. Users want web applications to behave like desktop installations but without the overhead associated with an installation. As more applications employ smart caching, anticipate user actions, and provide richer UI, the difference between web and desktop applications is becoming blurred. Expectations of web applications are rising. The end user has now seen that it is possible to avoid the commitment of installing a desktop application and still have a rich and responsive experience.

Why Developers Want AJAX

Often, the first question to arise when starting a new development project is what type of application it will be. Should it be a desktop application or a web application? This is a key decision because it has historically dictated a lot about the nature of the application and the development problem space. Many developers are now choosing to build web applications by default unless something about the application dictates that it must be a desktop install. If it must run offline or if it requires a user interface that is complex to achieve in HTML, targeting the web browser may be ruled out, and the choice to write a standalone application is forced.

Developers have a difficult job writing modern web applications due to the inherent worldwide-web functionality constraints imposed by the use of the Hypertext Transfer Protocol (HTTP) and the way browsers use it. HTTP is a stateless protocol. The web browser requests a page, possibly carrying some querystring or form input parameters, and the server processes the request and sends a response that includes HTML-rendered content. The server can only react to the information supplied in the current request and doesn’t know, based on the information in the request itself, details about the path the user took to get to the current view. When the response is rendered, the connection may be broken and the server won’t have any information to preserve for the next request. From the server’s perspective, it is simply listening for requests to come in from any browser anywhere and then reacting. The browser issues a request to the page and receives an HTML page in response. It uses the HTML it receives to render the user interface. The user interacts with the page, and, in response, the browser clears the screen and submits a new request to the server, carrying some information about user input or actions. Again, a complete HTML page is returned. The browser then presents the new version of HTML. Fundamentally, the HTTP protocol is stateless. The server gets a request and responds to it. The request carries limited information about the ongoing conversation that is happening between client and server.

AJAX makes this much better. AJAX breaks this pattern by updating portions of the page separately, via partial page rendering. Figure 1-1 shows a typical non-AJAX series of browser and server interactions. Each request results in a full page rendering, and, in response, the browser updates the user’s entire view.

In Figure 1-2, AJAX is employed to improve the user’s experience. A request is made for the initial page rendering. After that, asynchronous requests to the server are made. An asynchronous request is a background request to send or receive data in an entirely nonvisual manner. They are asynchronous because the user interface isn’t frozen during this time, and users can continue interacting with the page while the data transfer is taking place. These calls get just an incremental update for the page instead of getting an entirely new page. JavaScript running on the client reacts to the new data and updates various portions of the page, as desired. The number of requests to the server may be no different, or in some cases there may actually be more calls to the server, but the user perception is that the application feels more responsive. They aren’t forced to pause, even if it’s only a slight pause, and wait for the server while staring at a blank browser screen.

Almost a decade ago, the Microsoft Exchange Server team created an ActiveX control called XmlHttpRequest that could be instantiated from JavaScript and used to communicate with the server. This can occur without clearing the screen to paint a whole new page. Using the XmlHttpRequest object, you could send information to the server and get data back without requiring a whole new HTML page. JavaScript code could then manipulate the HTML dynamically on the client, avoiding the annoying flash and the wait that users associate with web browsing. This functionality was not limited to Internet Explorer for long. Soon, other browsers included XmlHttpRequest objects as well. Developers could now write richer applications with reach extending across various operating systems.

The browsers also created an advanced DOM (Document Object Model) to represent the browser, the window, the page, and the HTML elements it contained. The DOM exposed events and responded to input, allowing the page to be manipulated with script. Dynamic HTML (DHTML) opened the door to writing rich interfaces hosted within the web browser. Developers started writing hundreds and even thousands of lines of JavaScript code to make rich and compelling applications that would not require any client installation and could be accessed from any browser anywhere. Web applications began to move to a whole new level of richness. Without AJAX libraries, you would be faced with writing lots and lots of JavaScript code and debugging the sometimes subtle variations in different browsers to reach this new level of richness.

What Is ASP.NET AJAX?

ASP.NET AJAX is the name of Microsoft’s AJAX solution, and it refers to a set of client and server technologies that focus on improving web development with Visual Studio. Other companies have their own AJAX solution, often taking a radically different approach, but Microsoft has sought to build upon the popular ASP.NET technology by developing a comprehensive set of script libraries as well as server programming enhancements. One piece, the Microsoft AJAX Library, is a JavaScript library that works on a variety of browsers and serves to simplify JavaScript development. It provides you with the capability to easily write JavaScript using an object-oriented programming approach similar to code-behind programming in ASP.NET. You can use the functions of the Microsoft AJAX library to interact with the DOM, dynamically update portions of the page, communicate with the web server asynchronously, and write rich animations on the page. You’ll learn about the client features in Chapters 6 and 7, but for now think of the Microsoft AJAX Library as a type system and set of class libraries that simplify writing JavaScript to enhance the user experience, manipulate the DOM, and communicate with the web server. The huge benefit in using this library is that it abstracts the tedious low-level DHTML programming into an OOP model that is much easier to work with.

The other part of the ASP.NET AJAX release is the server-side ASP.NET 2.0 AJAX Extensions. These extensions build on top of the ASP.NET classes and controls and leverage the Microsoft AJAX Library sent to the browser. They make it easy to quickly take advantage of AJAX technologies to enrich an application. Through a set of standard web services, ASP.NET AJAX is also able to leverage server-based application services such as authentication and user profile storage. The extensions both extend some of the existing ASP.NET controls by adding new behaviors and include a new set of server controls that make it easy to do asynchronous updates to a page and leverage server resources.

The client and server pieces of ASP.NET are shown in Figure 1-3. ASP.NET is built on top of the Microsoft Internet Information Services (IIS) web server. ASP.NET AJAX builds on top of that and the web services it includes. The Microsoft AJAX Library runs in the browser to manipulate the DOM, communicate asynchronously with the web server, and take advantage of ASP.NET services.

The ASP.NET Component

The original (ASP) Active Server Pages technology was released as part of Internet Information Server 3.0. It was then improved with support for transactions and access to COM objects with the release of the NT 4.0 Option Pack almost ten years ago. At the time, most websites consisted of static HTML pages. To the extent that there were any dynamic applications, they were CGI (Common Gateway Interface) or ISAPI (Internet Server API) applications typically written in C and C++. With the release of Active Server Pages (ASP), developers could use JavaScript or VBScript on the server to leverage a set of intrinsic objects provided by ASP. “Classic ASP,” as it is now called, provided a session object so that developers didn’t need to worry about the stateless nature of HTTP. It had Request and Response objects that provided for easy access to data coming from forms on the client and a way to send updated information back. The Server and Application objects were an avenue for accessing information from the web server and utilizing a common set of COM objects across the application.

Although Classic ASP was a big win for developers, developers soon found that developing complex applications became difficult. The lack of support for modularization meant that applications ended up with such complex interdependencies in script that developers often referred to it as “spaghetti code.” Debugging support was severely lacking, and there were no rich design tools for developing applications. Performance also suffered because ASP used a slow scripting model, and syntax errors could only be detected at runtime. ASP.NET is a big leap forward. It provides compatibility for existing applications by including the same set of intrinsic objects found in Classic ASP but moves from interpreting JavaScript and VBScript on the fly to using a compiled set of pages and modules written in C# and VB.NET. Classic ASP simply executed script in order from the top to the bottom of the page; ASP.NET is an event-driven model with a page lifecycle, making it more like writing a desktop application. Now, instead of including separate JavaScript files to represent business objects, you can create objects in any .NET language and access them directly from ASP.NET.

ASP.NET takes a set of pages that contain code and markup and generates a Page class that is then compiled and cached. For each request to the page, the class is instantiated and a complete page lifecycle is executed. A set of events are executed, some of which have been overridden by the generated Page class. Controls in the page also participate in the lifecycle, databinding to backend databases, reacting to user input, and dealing with changes to their state from the user’s previous view. To react to user actions, the developer has only to provide an event handler for the given action. For example, the button control exposes a Click event. When using it, you don’t need to write code to examine all form variables on a page to know if the button was clicked. Instead, you just provide code for an event handler override. The event handler code can then update the HTML for the page or the properties and data of other controls on the page.

The JavaScript Component

AJAX technologies take advantage of the common support for JavaScript found in modern browsers. Because there is a standard that is supported across the various browsers, you can write scripts knowing that they will run. This wasn’t always the case.

In the mid 1990’s, Netscape and Microsoft (along with others) collaborated on a standard for a scripting language that they would support in their web browsers. The standard is called EcmaScript. Microsoft’s implementation is called JScript, but the language is generally referred to as JavaScript, as it was called in Netscape. (It has nothing to do with Java, but someone must have thought the association was useful for marketing purposes.) JavaScript program snippets are sent down to the browser along with the HTML, and they run inside the user’s browser to affect how the page is processed on the client.

JavaScript is not compiled; it is interpreted. There is no static type-checking like you get in C++ and C#. You can declare a variable without needing to specify a type, and the type to which the variable refers can change at any time. This makes it easy to get started programming in JavaScript, but there’s inevitably a certain amount of danger in allowing the data type of a variable to change dynamically at runtime. In the following snippet, notice that the variable can reference any type without difficulty:

var something = 1;
something = true;
something = “a string”;

JavaScript is a dynamic language. Types can actually be extended during program execution by other code. This means that you can write code that creates types on the fly. Because there is no enforcement of type safety, your code can receive these types as parameters or return values without any problem. This provides a great degree of flexibility and coding power.

The fundamental types in JavaScript are strings, numbers, Booleans, and functions. There is also support for objects and arrays, which are collections of the fundamental types. Some additional objects are included that are considered essential for many programming tasks. This includes support for regular expressions and date and time operations.

You can use the plus operator on strings in JavaScript to concatenate them:

var theEnd = “THE END.”;
var result = “Beginning, “ + “middle, and “ + theEnd;

In this example, the result variable is now the string: “Beginning, middle, and THE END.”

JavaScript interpreters use the IEEE floating-point standard for storing numbers. Ignoring the gory details, you can assume that for most programming tasks you won’t have any trouble.

The Boolean type in JavaScript is about what you would expect it to be but maybe not exactly so. The Boolean represents whether or not an expression is true, but it uses the C-style convention using integer values 0 and 1.

Variables can exist in JavaScript without having a value, and a variable may simply be undefined, which can produce unexpected results. In this piece of JavaScript, three variables are declared, and all of these comparisons are designed to return a true value.

You can check specifically to see if a variable has been defined like this:

if( typeof(undefinedVar ) == “undefined” )
{
alert(“undefinedVar is undefined”);
}

Variables can also have a null value, which is not the same thing as being undefined, as a null value does constitute a value.

Functions are also real types in JavaScript. They can accept arguments and return values. Functions can be passed to other functions and can be created dynamically by other script code.

Here are two equivalent definitions for a function called Add that will take two variables and return the result of applying the plus operator. Notice that I didn’t state that it takes two numbers. Remember, JavaScript variables don’t have a defined type, so I could just as easily pass two strings and get them concatenated by my Add function.

Once either of these styles is used to create a function, it can be called from that scope and any nested scope to perform the addition. There is no advantage to one of these forms over the other. You can simply choose to use the syntax that you prefer.

Objects and arrays are just collections of other types. Array types do not require that the values they hold be named; instead, you can access them by index. The values held in an object are referenced by field or property names. Objects can also hold functions (which can be accessor functions to give public visibility to local variables), which lets you create data structures that represent entities in JavaScript code. Missing from this sort of object-oriented programming is a concept of type inheritance. The Microsoft AJAX Library provides a set of classes and recommended patterns for achieving inheritance in JavaScript, making it more natural for switching between JavaScript and other high-level languages. The following code example includes a definition for an Album object that holds and returns the artist and album title. An array is then used to store information about several albums.

Packaging

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The packaging of ASP.NET 2.0 AJAX can be fairly confusing. The basics of the packaging are:

ASP.NET 2.0 AJAX Extensions 1.0—The ASP.NET 2.0 AJAX Extensions 1.0, also referred to as the RTM/Core code, is an independent download. This contains the functionality that will receive support from Microsoft in the initial release of the product. The source code is available.
ASP.NET AJAX Futures Community Technology Preview (CTP) — The ASP.NET 2.0 AJAX framework contains a set of functionality that is experimental in nature. This functionality will eventually become integrated with the RTM/Core code. During the initial release, the Futures CTP functionality will be a separate download from the RTM/Core bits. This will not receive specific support from Microsoft beyond community-based support. The CTP bits require that the RTM/Core bits already be installed for the CTP bits to be installed. The CTP is also referred to as Value-Added Bits.
Microsoft AJAX Library—The Microsoft AJAX Library is a set of JavaScript client libraries that make up the standard download to a web browser and provide much of the support for AJAX in the client. These libraries will work with a non-IIS server and are available as a separate download. This library is included in the ASP.NET 2.0 AJAX Extensions 1.0 download as well as being available as a separate download.
ASP.NET AJAX Control Toolkit — The AJAX Control Toolkit is a separate download that provides a set of client-side GUI widgets that integrate with the ASP.NET 2.0 AJAX framework. The toolkit is licensed separately from the framework and includes the source code for developers who would like to review the source.

Futures

It has already been announced that ASP.NET 2.0 AJAX will be integrated into the .NET framework and Visual Studio in the Orcas versions of these products. Future versions will undoubtedly have more integration between ASP.NET 2.0 AJAX, ASP.NET, and Visual Studio.

Summary

AJAX provides developers a foundation to build web-based applications with an improved user experience. In this introductory chapter, you have looked at the following:

Development from a historical perspective
Web development methodologies
Some of the features that ASP.NET AJAX provides, such as improved user responsiveness and decreased load on the web server
Multiple technologies that can improve the user experience
The general components in the ASP.NET 2.0 AJAX packaging
The problems ASP.NET AJAX solves, and who is using it

Understanding AJAX

AJAX is an acronym for Asynchronous JavaScript and XML. If you think it doesn't say much, we agree. Simply put, AJAX can be read "empowered JavaScript", because it essentially offers a technique for client-side JavaScript to make background server calls and retrieve additional data as needed, updating certain portions of the page without causing full page reloads. Figure 1.4 offers a visual representation of what happens when a typical AJAX-enabled web page is requested by a visitor

What Is ASP.NET 2.0 AJAX?

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On June 28, 2005, Microsoft announced “ASP.NET 2.0 AJAX.” ASP.NET 2.0 AJAX is an AJAX-oriented .NET library that runs on .NET 2.0. Though ASP.NET 2.0 AJAX is an AJAX library and can be used to perform AJAX operations, it is really much more. ASP.NET 2.0 AJAX offers many of the same types of features of the server-side ASP.NET, but it is directed at the client side. Because ASP.NET 2.0 AJAX is fully integrated with ASP.NET, it provides rich integration with the services provided by ASP.NET.

ASP.NET 2.0 AJAX provides the following features (and much more):

AJAX-style communications between client and server. This communication is over web services.
Asynchronous communication. All client-to-server communication in the ASP.NET 2.0 AJAX framework is asynchronous.
A set of server-side controls that enable rich client-side functionality.
A set of client-side controls and classes that further enable client-side functionality.
A framework for encapsulating client-logic through the creation of namespaces and classes.
Cross browser support. Although there is no official matrix of web browsers that ASP.NET 2.0 AJAX supports, the latest versions of Internet Explorer, Firefox, and Safari are supported. In addition, Opera is thought to be supported; however, we have not been able to find an official statement from Microsoft regarding this.

Running ASP.NET AJAX Applications

Unfortunately, not all web browsers ever produced will support ASP.NET AJAX. To run an ASP.NET AJAX application, a web browser must:

Be relatively modern — ASP.NET AJAX applications are not available in all versions of all web browsers. Though Internet Explorer version 6 and later, Firefox version 1.5 and later, and Safari provide support for these applications, older versions may be problematic because of their support for different versions of the other requirements.
Support the DOM — The capability to update form elements on a page based on new data is important. Accessing the controls in a standard way means that writing code that runs over a majority of web browsers is easier than having code that has a large number of if/then/else statements that are dependent on the browser version.

Support JavaScript — ASP.NET AJAX requires some amount of actions to occur out on the client. These actions are done using the JavaScript programming language. Because the major web browsers support JavaScript, it makes sense for JavaScript to be used for the client-side programming language.

Possibly have ActiveX enabled on the client — If you are using the Internet Explorer 6 browser while running on Windows, you may have problems if ActiveX is not enabled.

ASP.NET 2.0 AJAX falls into four areas:

Server-side controls — Server-side controls generate the appropriate client-side markup and script to perform client-side operations without the need for a postback. These controls provide a fairly easy environment to debug. For example, debugging with the UpdatePanel is fairly easy. Besides the UpdatePanel, other controls that work similarly are the ASP.NET AJAX Control Toolkit.

Client-side classes — These classes provide additional functionality to the client-side browser. This type of functionality is similar in concept to the base class libraries included in the .NET framework. An example would be the whole Sys.Net namespace along with the extensions to the base JavaScript objects.

Web services integration — This functionality allows a developer to use web services as the communication channel between the web browser and the web server without having to understand the differences between the MSXML component in IE and the XmlHttpRequest object in Firefox.

Technologies That Make Up AJAX

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AJAX is a general umbrella term. AJAX itself stands for Asynchronous JavaScript And XML. The term was coined by Jesse James Garret of Adaptive Path in an essay published in February 2005 (http:// www.adaptivepath.com/publications/essays/archives/000385.php) and was quickly accepted by the development community.

Based on this general umbrella term, take a look at the specific items that make up AJAX:

XMLHttpRequest — XMLHttpRequest allows the browser to communicate to a back-end server. This object allows for the browser to talk to the server without requiring a postback of the entire web page. With Internet Explorer 5 and 6, this capability is provided by the MSXML ActiveX component. With the Mozilla Firefox, IE 7, and other web browsers, this capability is provided by an object literally called XmlHttpRequest. The XmlHttpRequest object is modeled after the MSXML component and defined by the XMLHttpRequest standard from the W3C. The ASP.NET 2.0 AJAX client-side JavaScript libraries hide the differences between the various browsers.
JavaScript—JavaScript provides the capability to communicate with the back-end server. The version of JavaScript must be version 1.5 or later. Though JavaScript is not specifically required, it is needed from the standpoint that JavaScript is the only client-side scripting environment supported across the major modern web browsers. There are other client script languages; however, these are not supported across all browsers.
DHTML/DOM support—The browser must support the ability to dynamically update form elements, and the ability to do this in a standard way comes through the support for the Document Object Model (DOM). By supporting the DOM, it becomes easy for developers to write a single piece of code that targets multiple browsers.
Data transport with XML or JSON — Using XML allows for the ability to communicate with the web server in a standard mechanism. The default data format with ASP.NET AJAX is JSON.

What Is AJAX?

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So into this development environment comes a set of technologies that are collectively referred to as AJAX. If you are an “old guy” developer like me, then AJAX represents a similar concept to the client-server development mentioned earlier in the chapter. With client-server development, the amount of data transferred is minimized over a terminal application by transferring only the necessary data back and forth. Similarly, with AJAX, only the necessary data is transferred back and forth between the client and the web server. This minimizes the network utilization and processing on the client.

Advantages of AJAX

The advantages of AJAX over classical web-based applications include:

Asynchronous calls — AJAX allows for the ability to make asynchronous calls to a web server. This allows the client browser to avoid waiting for all data to arrive before allowing the user to act once more.
Minimal data transfer — By not performing a full postback and sending all form data to the server, network utilization is minimized and quicker operations occur. In sites and locations with restricted pipes for data transfer, this can greatly improve network performance.
Limited processing on the server — Along with the fact that only the necessary data is sent to the server, the server is not required to process all form elements. By sending only the necessary data, there is limited processing on the server. There is no need to process all form elements, process the ViewState, send images back to the client, or send a full page back to the client.
Responsiveness—Because AJAX applications are asynchronous on the client, they are perceived to be very responsive.

Context — With a full postback, users may lose the context of where they are. Users may be at the bottom of a page, hit the Submit button, and be redirected back to the top of the page. With AJAX there is no full postback. Clicking the Submit button in an application that uses AJAX will allow users to maintain their location. The user state is maintained, and the users are no longer required to scroll down to the location they were at before clicking Submit.

History of AJAX

For all its perceived newness and sexiness, the technologies that make up AJAX are really not new. The ability to communicate back to the server through a hidden frame without posting the main page back to the server has been around for a long time. Communication between client and server has been available— back to the release of Internet Explorer’s ability to script ActiveX controls on the client browser and to the MSXML component, both of which date back into the late 1990s. Personally, I saw the first formal usage of client script and MSXML in 2003. The problem with the technology at that time was the need to manually create the necessary client-side JavaScript. In 2003, there was too much code overall that had to be written and too much custom code that had to be written to get this to work. Only since the second half of 2005 have client-side libraries and server-side support for ASP.NET started to make their presence felt and been used significantly.

The mainstream development community has only recently started using the technique. The release of Google’s Suggest and Maps are what really opened the eyes of the users to the development technologies. These applications sent a shockwave through the development community.

Explain ASP.NET Ajax Framework.

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Answer
ASP.NET Ajax Framework is used for implementing the Ajax functionality. It allows you to create interactive web applications which can update data on the web page without changing the actions of the existing page. The frame work includes both client and serer side components. The framework can be used best in ASP.NET 2.0.

Explain limitations of Ajax.

Answer

Back functionality cannot work because the dynamic pages don’t register themselves to the browsers history engine. Hence the need of Iframe becomes essential.
The page cannot be bookmarked if implemented using Ajax.
If java script is disabled , Ajax will not work
Because different components of the pages are loaded at different times, response time may be slow.
Because different components of the pages are loaded at different times it may create confusion for the user.

What is the role of Script Manager in Ajax?

Answer
Script Manager, as the name suggests is used to manage the client side script of Ajax. Since Ajax uses Java Script, there needs to be a mediator to manage this script and restrict a particular version to a browser. A Script manager is present on every page where Ajax is used to enable the Ajax Libraries. These Libraries in turn helps to implement the core Functionality of Ajax: Partial rendering.

List out differences between AJAX and JavaScript.

Answer
Ajax is Asynchronous Java Script and XML. Here on sending request to the server, one needn’t wait for the response. Other operations on the page can be carried out. Hence, Asynchronous. On the other hand, Java script sends an HTTPRequest to the server and waits for the XML response.

E.g. populating State field. Using JavaScript we need to use the “Onchnage” event where as using ajax, the request is just sent to populate the state list. Other operations can be carried out on the page.

Ajax is a part of Java Script programming. Java Script is used to manage and control a web page once downloaded. Ajax does not need to wait for the whole page to download.

Use of Ajax can reduce connections to the server since the script has to be requested once

Describe how to create AJAX objects.

Answer
Ajax Objects can be created by the following syntax:

Var ajax= New ajaxObject(‘page path’). Here page path is the URL you want the Object to call. The URL must be of the same domain as the webpage.

Define JSON.

Answer
JSON is JavaScript Object Notation. JSON is a safe and reliable data interchange format in JavaScript. This format is easy for humans to read and machines to understand.

Explain in brief abo XMLHttpRequest object.

Answer
XMLHttpRequest object is used to transfer data between a client and a server. Here the client can be a web browser. Here, the client can send and receive data without reloading the page.

It can be created as follow

Var request = new XMLHttpRequest ()

Describe the formats and protocols used by AJAX.

Answer

Ajax uses HTTP’s GET or POST. AJAX also uses XMLHttpRequest protocol for requesting to the web server.
AJAX uses JSON format to communicate between client and server. UED or URL encoded data formats can also be used.

What are the security issues with AJAX?

Answer
AJAX function calls are sent in plain text to server. These calls may easily reveal database details, variable names etc

User’s browsing session can be monitored my maliciously inserting scripts

Ajax may encourage developers to use multiple server side pages thereby introducing multiple entry points for attackers

Ajax security issues posted on March 12, 2009 at 22:35 pm by Rajmeet Ghai.

Are there any security issues with AJAX?

A JavaScript can not access the local file system without the user's permission.
An AJAX interaction can only be made with the servers-side component from which the page was loaded.
A proxy pattern could be used for AJAX interactions with external services.
The application model should not be exposed as some user might be able to reverse engineer the application.
HTTPS can be used to secure the connection when confidential information is being exchanged.

Describe how to handle concurrent AJAX requests.

Answer
JavaScipt closures can be used for handling concurrent requests. A function can be written to handle such requests. Once processing of code is over, URL and the call back function to call can be passed as parameters. These parameters are passed to the AJAXInteraction(url, callback) object. Closures insure that the proper callback function associated with a specific AJAX interaction is called.

When should AJAX NOT be used?

Answer

If the page is expected to be shown in a search engine like Google. Since Web crawlers don’t execute javascript code.

If the browser does not support JavaScript.

If security is a big concern in the application; Since Ajax allows end user to see half of what’s being sent to the server.

How do you know that an AJAX request has completed?

Answer
By determining the readyState property value of XMLHttpReqyest, One can know if the request is completed. If the readyState value = 4, the request has been completed and the data is available.

How do I handle the back and forward buttons?

Answer
In order to store changes in the browsers web history (enabling back and forward buttons) Iframes can be used. Iframes allow am HTML document to be embedded in another HTML document.

RSH (Really Simple History) framework can also be used. RSH framework explains the management of bookmarks and history for Ajax applications.

What is AJAX and what problem does it solve?

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Answer
Ajax is a set of client side technologies that allows asynchronous communication between client and web server. In synchronous communication, complete round trip happens with each request/response action event when small data of the page to be refreshed. Ajax has solved this problem of posting entire information every time through asynchronous communication.

XmlHttpRequest is the basic fundamental behind Ajax. This allows browser to communicate with server without making post backs.

What are the benefits of AJAX over Java applet?

The following are the benefits of AJAX over Java applet:

AJAX applications are loaded in seconds, where as Applets takes longer time. The reason is, Applet applications are tend to load large libraries.
AJAX provides standard look and feel for web applications, where as Applets provides GUI based look and feel.
AJAX features can increase from a conventional web application, where as Applets uses complete programming process right from the scratch.
Java version changes enable incompatibilities between Applet and java environments used by the browser, where as in AJAX incompatibilities are not the constraints.

What is the disadvantage of AJAX?

The disadvantages of AJAX are:

Search engines would not be able to index an AJAX application.
The server information can not be accessed within AJAX.
AJAX is not well integrated with any browser.
ActiveX requests are enabled only in IE 5 and IE6
Data of all requests is URL-encoded, which increases the size of the request.

How is encoding handled in AJAX?

AJAX encoding can be done in two ways:

encodeActionURL() method is used for full page refresh
encodeResourceURL() method is used for partial page refresh.

Why is AJAX a comfortable fit with JAVA?

AJAX is a comfortable fit because, using Java Enterprise Edition the following tasks can be performed:

AJAX client pages can be generated to server incoming AJAX requests
Server side state is managed for AJAX clients
AJAX clients can be connected to enterprise resources.

What is synchronous request in AJAX?

Synchronous AJAX is a process that makes a java script to halt or stop the processing an application until a result is sent by a server. The browser is frozen, while the request is processed. The response time is 99.99% quick and fast enough. In case of intrusion for a request or transfer of the file, the browser freezes may be for two minutes until the time is out for the request. The advantages of using synchronous AJAX are, simple to code and can be used in the events ‘onunload’ and ‘onbeforeunload’

When should I use a Java applet instead of AJAX?

Applets provide features like custom data streaming, graphic manipulation, threading, and advanced GUIs which AJAX cannot.
However, with the help of DHTML, the functionalities of AJAX can be extended further.
AJAX requires that the browser be DHTML and AJAX capable.
AJAX-based functionality does need to take browser differences into consideration due to which using a JavaScript library such as Dojo which abstracts browser differences is recommended.
AJAX/DHTML works well for applications where the latest browsers are used.

How Ajax is different?

An AJAX application introduces a layer between the user and the server which comprises of the AJAX engine. This eliminates the adhoc interaction between the client and the server and makes the application more responsive.

A browser loads an AJAX engine instead of the web page and then communicates with the server on users behalf as well as provides the user with an interface.

As the communication with the server in AJAX is asynchronous, the user doesn’t have to wait for a server response.

Is the server or the client in control in AJAX?

With AJAX the control can be more centralized in a server-side component or a mix of client-side and server-side controllers.

Centralized server-side controller
In this type of architecture, the controller ensures that the data on the client and the server are synchronized.
Client and server-side controllers
In this type of architecture the presentation related control, event processing, page manipulation, and rendering of model data is done through Javascript on the client side.
The server-side is responsible for business logic and pushing updated model data to the client.
Both methods are viable depending on the kind of task. However, the centralized server side controller is preferred as in the other case (Client and server-side controllers) the server might not have the knowledge of the state of the client page.

Are there Usability Issues with AJAX?

The nature of updating a page dynamically using data retrieved via AJAX interactions and DHTML may result in drastically changing the appearance and state of a page.

Since the pages get updated dynamically, the state of a page may not remain the same.
So the behavior of a page may need to be defined in each of the following user actions:

Navigation using the back or forward buttons of the browser
Book-marking a page
Sharing a URL
Printing a page at any given time

Navigation:
The output of the user actions like a page refresh, forward or back navigation, etc need to be defined.
In this case using a JavaScript framework such as Dojo that provides API's history manipulation and navigation control would be simpler.

Book-marking and URL sharing:
Dojo provides client-side interface for book-marking and URL manipulation.

Printing:
Issues could arise while printing dynamically rendered pages.

RSS interview questions

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What is RSS? Explain the purpose RSS?

RSS stands for Really Simple Syndication / RDF Site Summary / Rich Site Summary.

The frequently updated work like the blog entries, news headlines, audio, and video need to e published in a standardized format. RSS is a family of such Web feed formats. An RSS document is also called a feed, web feed or a channel. It comprises of full or summarized text as well as metadata (dates and authorship).

The purpose of the RSS is to let the publishers join the content quickly and automatically. It also benefits the readers who need timely updates from specific websites. The initials "RSS" are used to refer to the following formats: " (RSS 2.0)", " (RSS 0.91)".

Explain how RSS Works with an example.

With the help of RSS, the website authors can maintain a list of notifications on their website in a standard way.

This list can also be used to find out the latest updates even by people.

The RSS aggregators are used to automatically access the RSS feeds and organize the results per your criteria.

Describe the steps to get your RSS file up on the web.

Authors add the content on the website through the content management programs. These programs have a publish facility that creates the HTML files.

These programs can even update the RSS feed XML file simultaneously. Thus they add an item that refers to the new content and then they remove old content.

Authors who do not use special tools maintain the XML files on their websites by themselves

Some services even read requested websites themselves periodically and then determine changes automatically.

Explain RSS Element.

The element describes the RSS feed and usually contains one or more elements which define the content in the RSS feed.

Explain child elements of . i.e. The Element, The Element, The Element, The Element

Child elements of has three required child elements:

which defines the title of the channel like a home page. <link> which defines the hyperlink to the channel. <description> which describes the channel.<o:p></o:p> Other than these there are child elements like:<o:p></o:p> <category> specifies a category of a feed <copyright> notifies about copyrighted material <image> allows an image to be displayed when aggregators present a feed <language> specifies the language used to write a document<o:p></o:p> <h4 style="line-height:11.25pt">What Is RSS (Really Simple Syndication)? <o:p></o:p></h4> RSS is a web based format that is used to display content that is frequently updated. News, weather reports, blogs etc are examples of such content. The Web format is specified using XML. This XML is based on a standard web format that allows the information to be published once and viewed by many different programs.<o:p></o:p> <h4 style="line-height:11.25pt">Why syndicate your headlines with RSS?<o:p></o:p></h4> <ul type="square"> <li class="MsoNormal" style="color:black;mso-margin-top-alt:auto;mso-margin-bottom-alt: auto;line-height:11.25pt;mso-list:l0 level1 lfo1;tab-stops:list .5in">RSS is a simple mechanism to generate updated data which can be customized with online portals.<o:p></o:p></li> <li class="MsoNormal" style="color:black;mso-margin-top-alt:auto;mso-margin-bottom-alt: auto;line-height:11.25pt;mso-list:l0 level1 lfo1;tab-stops:list .5in">A website that publishes some news, blogs can use another website headlines using RSS.<o:p></o:p></li> <li class="MsoNormal" style="color:black;mso-margin-top-alt:auto;mso-margin-bottom-alt: auto;line-height:11.25pt;mso-list:l0 level1 lfo1;tab-stops:list .5in">RSS files can be automatically updated.<o:p></o:p></li> <li class="MsoNormal" style="color:black;mso-margin-top-alt:auto;mso-margin-bottom-alt: auto;line-height:11.25pt;mso-list:l0 level1 lfo1;tab-stops:list .5in">RSS data is small and loads fast.<o:p></o:p></li> </ul> <h4 style="line-height:11.25pt">Explain the Relation between RSS and XML?<o:p></o:p></h4> XML or Extensible Markup Language is used to organize generic information with tags in a structured document. Really Simple Syndication is an extension of XML is used to o organize headlines of news. RSS formats are specified using XML and can be considered as an extended schemas of XML.<o:p></o:p> <h4 style="line-height:11.25pt">Describe how to create an RSS file.<o:p></o:p></h4> RSS files use XML as the language to create files. Any RSS file has a number of tags which must be closed properly. The RSS file once complete, must be validated.<o:p></o:p> <ul type="square"> <li class="MsoNormal" style="color:black;mso-margin-top-alt:auto;mso-margin-bottom-alt: auto;line-height:11.25pt;mso-list:l3 level1 lfo2;tab-stops:list .5in">To start with the RSS file needs to have a Title, Description and a link. Example: The RSS and the channel tag needs to be opened following which the RSS feed tags are placed. <?xml version="1.0" encoding="ISO-8859-1" ?> <rss version="2.0"> <channel> <title>This is a sample website
http://www.sample.com
Sample website
en-us

The file now needs to be saved with a .xml extension.

Review the RSS file for any special characters that XML does not accept like “&:. Such characters need to be escaped.

The feed now needs to be validated. If the validator finds any problems in your feed, it will give you messages for each type of problem and highlight where the problem first occurs in your feed.

Benefits to RSS

Ability to publish latest updates to the readers.
RSS displays the news and headlines to overwhelm the user. If the user wants details, he can click on the link of the actual content.
RSS has the ability to control the flow of information users receive
If the user feels that the content quality is not acceptable, he just needs to remove the feed from the RSS reader to avoid any content being read from that source.
Allows user to scan information from different sources.
Can be typically used for weather reports, blogs, headlines, discounts,

Why Create RSS?

RSS is a very strong technology used to display latest information from various sources.
RSS can be considered as the most acceptable standard to publish news.
RSS can be used to increase site traffic since different contextual information can be displayed.
RSS is simple to create. RSS can be used as a source of income on the site as well.
Allows user to subscribe or unsubscribe content coming from different sources in a simple manner.

Explain the disadvantages of RSS.

Graphics and photos are not supported by ALL RSS feeds.
RSS feeds don’t display the actual URL or name of the website. This may confuse the user.
Publishers can’t determine the number of users who must have subscribed using its feed.
Publishers cannot know the reason why some feeds were unsubscribed.
Creates more traffic on the site and server.
Finding RSS feeds can be difficult as they may not appear in search results.

RSS more effective than Email. Comment

RSS avoids the problem of Spam commonly observed in Emails. If the spam filter is ON, it may cause important emails to be rejected. This problem is avoided in RSS since the messages will always reach their intended target as it is with the help of RSS reader or RSS aggregator that fetches the messages.

Explain how to use RSS as an autoresponder with RSS Autopublisher.

An autoresponder is used to deliver messages to people who request them. The messages are delivered in a sequential manner. The RSS autoresponders work the same as email autoresponders except that they are used to deliver messages and not emails. The RSS autoresponder will send out messages in a timely manner as specified by the user. Campaign and sales messages are common scenarios where aurotresponder needs to be used. RSS autopublisher is used to publish the autoresponder messages as well as usual RSS feeds.

What is the difference between news aggregators and feed readers?

RSS feed readers and news aggregators are almost the same and used for reading feeds. News aggregators are used specifically to view news related feeds but technically can read any feeds.

What Is Atom in RSS?

An Atom is a XML document used to describe related information which is known as feeds. This document can contain elements or attributes from other XML namespaces. Atom is most commonly used for syndication of Web content such as Weblogs and news headlines to Web sites.

An example of RSS document with explanation.

The first line defines the XML version and the character encoding used in the document. The next line defines the version of RSS. The element is used to describe the RSS feed. The element has three tags; , <link> and <description>.<o:p></o:p> <?xml version="1.0" encoding="ISO-8859-1" ?> <rss version="2.0"><o:p></o:p> <h2 style="line-height:11.25pt"><channel> <title>This is a sample website
http://www.sample.com
Sample website
en-us

XSLT and XPATH

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What is XSLT?

XSLT stands for XSL Transformations and is a language used to transform XML documents into XHTML documents or to other XML documents.

What are the roles of XSLT?

The roles of XSLT are:

XSLT is used to transform an XML document into another XML document such as HTML, etc.
XSLT can be used to add or remove elements and attributes to or from the output file.
XSLT can also be used for rearranging and sorting elements.
It can also be used for performing tests and making decisions about hiding and displaying of elements.

XSLT and XPATH-

What is XSLT? Explain its relationships with XSL.

XSLT stands for eXtensible Stylesheet Language Transformations. It is a language used to convert XML documents to XHTML or other XML documents. This conversion is done by transforming each XML element into an (X)HTML element.. it uses XPath to find information in a XML document. XSLT is nothing but transforming XSL’s. Xpath defines the parts of the source document that must match one or more predefined templates. Once a match is found, XSLT will transform the match into the result document.

What is XSLT stylesheet?

XSL stylesheet is just like a XML document used as a program text or a source. It contains sets of rules and instructions used for transformations. XSLT stylesheet along with the XML source documents are the inputs to the XSLT processor. The template rule contains two parts: a pattern used to match the nodes in the source document and a template which can be instantiated to form part of the result tree. A stylesheet is represented by an xsl:stylesheet element in an XML document.

Discuss the role of XPATH.

XPATH is used to scan the XML document for navigation of elements and attributes. It contains a library of standard functions string ad numeric values. For navigation, XPATH makes use of path expressions to select nodes or sets of nodes in a XML document.

Explain the XSLT data model.

XSLT shares the same data model of XPATH with some additions. XSLT accepts a XSLT stylesheet as an input and output is another XML, text or another document. The model is based on text nodes. These text nodes are embedded within element nodes. The model is a hierarchical structure like a tree. The tree has a variety of nodes like- text nodes, attribute nodes, element nodes, comment nodes, and processing instruction nodes. For every node type there is a way of determining a string-value for a node of that type.

Why the need for XHTML?

If a script in an HTML document is not well formed, small devices like mobile phones fail to display the content properly. Also, upgrading all the browsers to support XML is a timely affair. An intermediate solution is XHTML that is a combination of HTML and XML. In XTML the content has to be well formed so that there is no bad HTML.

XHTML vs HTML

XHTML
Elements must be properly nested
Elements must be closed
Elements must be in lowercase
Documents must have one root element

HTML
Elements need not be properly nested
Elements need not be always closed
Elements need not be in lowercase
Documents need not have one root element

Explain the XHTML syntax rules.

Some Syntax rules that need to be followed with XHTML are:

That Attribute names must be in lower case, their values must be in quotes and their minimization is done away from usage.

Also the ‘name’ attribute has been replaced by the ‘id’ attribute. The XHTML DTD defines mandatory elements.

What is the XMLHttpRequest Object?

The XMLHttpRequest object is used to connect to the server through http. Scripts use it to do so programmatically.

The EventTarget interface needs to be implemented if an object implements the XMLHttpRequest interface. Also, an XMLHttpRequest() constructor needs to be provided by objects that implement the Window interface.

Explain common XMLHttpRequest Object Properties. i.e. onreadystatechange, readyState, responseText, responseXML, status, statusText.

The ‘onreadystatechange’ property fires at every state change event.
The ‘readyState’ property is an object status integer. It uses the integers 0 to 4 for uninitialized, loading, loaded, interactive and complete states.
The ‘responseText’ property is a string version of data returned from server process.
The ‘responseXML’ property is DOM-compatible document object of data returned from server process.
The ‘status’ property is for returning numeric codes from the server like error codes, etc.
The ‘statusText’ property is used for string messages that accompany the status code.

Explain common XMLHttpRequest Object Methods.

The abort() is used to stop the current request.
The getAllResponseHeaders() method is used to return the full set of headers as a string.
The getResponseHeader("headerLabel") method is used to return the string value of a single header label.
The open("method", "URL"[, asyncFlag[, "userName"[, "password"]]]) is used to assign the destination URL, method, and other optional attributes of a request.
The send(content) method transmits the request, optionally with postable string or the data of DOM object.
The setRequestHeader("label", "value") method is used to assign a label/value pair to the header to be sent with a request.

What is the DOM?

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DOM is a platform independent, World Wide Web Consortium (W3C) standard form of representation of structured documents as an object-oriented model. It is an application programming interface so as to access HTML and XML documents.

What is the HTML DOM?

The HTML DOM API specializes and adds the functionality to relate to HTML documents and elements. It addresses the issues of backwards compatibility with the Level 0 of DOM and provides mechanisms for common and frequent operations on HTML documents.

What is the XML DOM?

Microsoft’s MSXML DOM provides an API for working with XML data. It also provides a programmatic representation of XML documents, fragments, nodes, or node-sets. It is a W3C standard form of XML representation. XML DOM objects can be used in XML applications written in C/C++, VB, VBScript and JScript.

What is the XMLHttpRequest Object?

The XMLHttpRequest object is used to connect to the server through http. Scripts use it to do so programmatically.

XSL-FO -

What is XSL-FO?

XSL-FO stands for Extensible Stylesheet Language Formatting Objects. It is used to format XML data and is also a W3C recommendation.

What is XSL-FO Documents? Explain XSL-FO Documents structure.

XSL-FO documents are XML files (.fo / .fob OR .xml – for being accessible by XML editors) with output information about the layout and contents.

Document Structure:
As usual they need to start with the version and the encoding declaration:

Namespace attribute can be written as:
-----------------Root element of XSL-FO documents. You can have the whole document within these tags.
----------------Contains page templates
----------------Contains a single page template
------------------------Describes the page contents

What is XSL-FO Processors?

XSL-FO processors (e.g. XSL Formatter, Xinc Beta Release, Scriptura) are programs that format XSL document output.

Most of them can also output PDF documents, quality print, HTML etc.

XML Attributes

Explain XML Attributes with an example.

The attributes in XML provide additional information about elements. Take a look at the following example:

”>

XML Elements vs. Attributes.

XML elements as well as attributes can be used to provide the same information about an entity in an XML database. The only difference lies in the way they are written. For example:

..... is an example of using attributes.
The same information can be provided in the element form as follows:

Da Vinci Code

What are the problems with using XML attributes?

It is preferred storing the data using the XML elemental form as it becomes very convenient to access and modify the data. Also the use of attributes is limited as they cannot contain multiple values, cannot contain tree structures nor are expandable

What are XML indexes and secondary XML indexes?

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Answer
The primary XML index is a B+tree and is useful because the optimizer creates a plan for the entire query.

It is always better to split the entire XML columns into relational rows and columns.

The primary XML index contains one row for each node in the XML instance.

The secondary XML indexes can be created to enhance the performance.
There are the types of secondary indexes:

PATH secondary XML index
If the use of path expressions on XML columns is prominant, the PATH secondary XML index can speed up the task.

VALUE secondary XML index
The VALUE index can be used if your task involves quering unknown attribute names.

PROPERTY secondary XML index
Clustering paths within each XML instance in the PROPERTY index can be beneficial when multiple values are retrieved from individual XML instances.

What is the purpose of FOR XML in SQL Server?

Answer
SQL Server 2000 provides the facility to retrieve data in the form of XML with the help of the FOR XML clause appended to the end of a SELECT statement.

There are 3 types of FOR XML modes — RAW, AUTO, and EXPLICIT.

They all generate a different style of XML document

What is the OPENXML statement in SQL Server?

Going through thousands of lines of XML degrades performance to a great extent.This is where the OPENXML function comes into use. It does the parsing work for you quite efficiently.

The syntax of OPENXML is:

OPENXML(idoc int [in],rowpattern nvarchar[in],[flags byte[in]]) [WITH (SchemaDeclaration | TableName)]

OPENXML function is supposed to be used with two system stored procedures:

1.sp_xml_preparedocument
2.sp_xml_removedocuments

What is XML Serialization and Binary Serialization?

2010-02-08T05:49:00.001-08:00

Answer
XML Serialization makes it possible to convert any common language runtime objects into XML documents or streams and vise versa.

The XML Serialization enables it to convert XML documents into such a meaningful format that the programming languages can process the converted documents with ease.

Binary serialization converts the files to a binay format. In this case all the data get converted into a binary format which is not a human readable format. In binary serialization entire object state is saved, instance identity is preserved and it graphs with multiple references can be handled in this.

XML serialization doesnt allow these things.

XML Serialization

What is XML Serialization and Binary Serialization?

XML serialization is all about serializing an object into an XML file. Being an XML file is a flat text file, the file can be viewed, shared by another application. It is a stream of characters.

XML serialization is called shallow serialization because it can serialize only public objects.

Binary serialization is all about serializing an object into a Binary file. Being a binary file is a compact file and cannot be seen like a text file. In binary serialization, image objects can also be serialized. It is a stream of bytes.

Binary serialization is called Deep serialization because it can serialize the object containing references to the other objects.

In Binary serialization the entire object state is saved where as in XML serialization only some of the object data is saved.

What is XML Namespace?

2010-02-08T05:48:00.001-08:00

A namespace is a qualified name that is associated with the XML DTD / Schema location. The prefix ‘xmlns’ to a tag specifies the namespace of that tag. Usually the namespace tag is defined in the beginning tag of an element.

What is XML data binding?

Answer
XML data binding refers to the process of representing the information in an XML document as an object in computer memory.

The limitations of data binding include round tripping of elements and attributes. XML data binding product generates documents that are invalid because of sibling order. They do not preserve physical constructs. They do not preserve comments and processing instructions.

What is an XML encoding error?

Answer
XML documents can contain non ASCII characters, like Norwegian æ ø å , or French ê è é which introduce errors.

The 2 types are:
An invalid character was found in text content.
Switch from current encoding to specified encoding not supported.

You can avoid these errors by specifying the XML encoding Unicode.

Explain the difference between DOM and SAX.

2010-02-08T05:47:00.000-08:00

Answer
SAX parser works incrementally and generates events that are passed to the application. DOM parser reads the whole XML document and returns a DOM tree representation of xml document

In DOM the xml file is arranged as a tree and backward and forward search is possible In SAX traversing in any direction is not possible as Top to bottom approach is used.

SAX is essentially an API for reading XML, and not writing it. DOM allows you to read and write.

XML DOM and SAX -

Explain the features of DOM.

DOM is Document Object Model. It is used to read data from a XML document. It is more commonly used in applications where data in the document needs to be repeated accessed. DOM supports navigation in any direction. XML DOM is typically used for XML documents. The DOM defines the objects and properties of all document elements, and the methods (interface) to access them.

What is SAX? Explain its features.

SAX is Simple API for XML. It is used to read data from a XML document. A parser that uses SAX parses the XML serially. The API is event driven and these events are fired when the XML features are encountered. XML parsing is unidirectional. Memory used by a SAX parses is relatively low. Due to the event nature of SAX, the parsing is faster of an XML document.

What is XML Namespace?

Answer
An XSL sheet or a document may have duplicate elements and attributes. Therefore, the XML namespaces define a way to distinguish between duplicate element types and attribute names.
An XML namespace is a collection of element type and attribute names. It is a URI due to which any element type or attribute name in an XML namespace can be uniquely identified.
It consists of two parts : the name of the XML namespace and the local name.

e.g.: xmlns: h=”http://www.abc.com”
After this, you can write

……..

to associate the table with the declared namespace.

What is XML?

2010-02-08T05:46:00.000-08:00

Answer
XML, Extensible Markup Language, is an open, text based markup language that provides structural and semantic information to data. XML is a metalanguage that can be used to create other language. It is used to structure and describe data that can be understood by other applications. Using XML, we can separate the user interface from data.

Features of XML
XML is a generalized markup language that means one can define his/her own tag sets.
A valid XML document contains rules and is self-describing.
The rules that are found in DTD allow the documents to be validated.

Describe the logical structure of XML.

Answer
XML documents comprise of declaration, elements and comments

XML Declaration
It identifies the version to which XML conforms

Document Type Declaration
It consists of markup code that indicates grammar rules or Document Type Definition (DTD) for the particular class of document.

This statement tells the XML processor that the document is of the class Car that conforms the rules specified in the DTD "cr.dtd".

Document element
The document element contains data of an XML document.

Why is XML so popular?

Answer
Due to the following advantages of using XML, it has become popular:

It supports Unicode. Therefore documents written in any human language can be communicated.
Data structures: records, lists and trees can be represented using XML.
Its format describes structure, field names and their specific values too. Its therefore called self-documenting.
Its syntax and parsing requirements make the necessary parsing algorithms very simple, efficient, and consistent.
It can be used as a document storage and processing format.
It is platform-independent.

Why is XML referred as self-describing data?

Answer
Text labels inside of XML's syntactic delimiters that cause most people to think that XML is self-describing. But these tags aren't part of XML.

Choosing the terms used for tags or naming anything is often a difficult and contentious activity. Everyone naturally creates names that make sense to them.

However, XML is not self describing.

Why is XML extensible?

Answer
Extensibility is another attribute of XML. XML is short of "eXtensible Markup Language. This is so because a developer may easily create his own XML syntax for any applications he wishes to use it for. Any other developer, once having learned how to use his own language's XML parsing routines, can use any XML-based format currently available.

XML is a secured language for information exchange over the network. Explain

Answer
Applications require a secure exchange of structured data. XML encryption can ensure this by providing end-to-end security as it is iitself a widely used data structuring technology.

XML encryption addresses the issues not covered in by the TLS which are encrypting part of the data that is being exchanged and secure sessions between multiple parties.

XML Encryption can handle XML as well as binary data.

List the rules to be followed by an XML document.

Answer
Following rules need to be followed by an XML document:

They must have a root tag, the document should be well formed : the tags should be properly closed, since XML is case sensitive, one should take care that the documents are written with proper care and the attribute values should be inside “”

Explain about XML Canonicalization.

Answer
Canonicalization refers to finding the simplified form of an XML document.

XML files may not contain the same sequence of characters (bytes or octets) even if they are logically equivalent. This is where we need to canonicalize them and check their canonical forms.

Steps to canonicalize an XML document

Encoding schemes should represent characters by octets.XML documents should be encoded in UTF-8 encoding.
The canonical form needs all line breaks to be #xA.
All attributes need to be normalized in canonical form.

Define DTD (Document Type definition).

Answer
DTD - Document Type Definition defines the legal building blocks of an XML document.

It defines the document structure with a list of legal elements and attributes.

XML DTD is a rule book that an XML document follows. Once DTD is ready, you can create number of XML documents following the same rules specified in the DTD. DTD can be internal or external DTD. The internal DTD is included in the XML document, while external DTD exists outside the content of the documents.

Explain DTD and schema.

Answer
A DTD provides a list of the elements, attributes, comments, notes, and entities contained in an XML or HTML document and indicates their relationship with each other.

The 'DOCTYPE' tells the browser that it is a Document Type Declaration

Some commonly used attribute types are

CDATA The value is character data
ID The value is a unique id
IDREF The value is the id of another element
IDREFS The value is a list of other ids

Schema means the organization and the structure of a database.

E.g.: An XML schema is a description of XML document. It is expressed in terms of constraints on the structure and content of documents.

XML XML DTD

Define XML DTD.

What is a CDATA section in XML?

Answer
CDATA - (Unparsed) Character Data
The term CDATA is used when you dont want some text data to be parsed by the XML parser.

A CDATA section starts with "":

XML - CDATA section in XML

What is a CDATA section in XML?

The CDATA section of XML is used to describe the text that should not be parsed by the XML parser.

The characters like "<" ">" are not supported in XML
"<" will cause an error by the parser. Because the parser identifies <>

Any text that is included in CDATA section is ignored by the parser.
Example :
are used to enclose an element in XML "]]>

What is XSL?

Answer
XSL is a language for expressing style sheets. An XSL style sheet is a file that describes the way to display an XML document.

Using XSL stylesheets, we can separate the XML document content and its styling.

An XSL style sheet begins with the XML declaration:

defines that the document is an XSLT style sheet document.
The element defines a template.

Define CSS and XSL.

Answer
XSL is a language for expressing style sheets. An XSL style sheet is a file that describes the way to display an XML document.

Cascading Style Sheets is an answer to the limitations of HTML, where the structure of documents was defined and not the display. CSS formats documents for display in browsers that support it.

How do you display XML with XSLT?

Answer
First you need to declare the XSL style sheet:

xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

Then,
you create an XSL Style Sheet with a transformation template.
Add the XSL style sheet reference to your XML document to link them.

What is XQuery?

Answer
Xquery is a query language that is used to retrieve data from XML documents.

XQuery is a way to query the XML data, It is built on XPath expressions and is supported by quite a few database engines.

It can find and extract elements and attributes from XML documents.

XQuery is written in FLWOR fashion which stands for: For, Let, Where, Order by, Return

An example of XQuery is:
for $x in doc("abc.xml")/abc_name
where $x/a>30
order by $x/b
return $x/c

What is XPATH?

Answer
XPath is a language that describes how to locate specific elements (and attributes, processing instructions, etc.) in a document.

An XSL sublanguage designed to uniquely identify or address parts of a source XML document, for use with XSLT.

It is based on a tree representation of XML document. It provides the ability to navigate around the tree and to select the nodes by a variety of criteria.

The simplest XPath is /A/B/C where C is the child of B, B child of A

What is XMLA ?

XML for Analysis,
It is a Microsoft specified XML-messaging-based protocol for exchanging analytical data between client applications and servers using HTTP and SOAP as a service on the Web.

What is DOM?

Answer
DOM is an interface-oriented Application Programming Interface. It allows for navigation of the entire document. A DOM document can be created by a parser, or can be generated manually by users. Data types in DOM Nodes are abstract. DOM implementations generally require the entire document to be loaded into memory and constructed as a tree of objects before access is allowed. DOM is supported in Java. Its specification is regulated by the World Wide Web Consortium.

How do you assign object properties in JavaScript?

2010-02-08T05:45:00.000-08:00

JavaScript window Object Properties

window.closed - indicates whether a window has been closed or not.

window.defaultstatus / window.status - specifies the default message / message displayed in the browser status bar.

window.frames[] - This array holds the array of frame objects of the window

window.name - Contains the name of the window object. (Windows opened by a script need to have a name)

window.opener - contains a reference of the parent window which opened it.

window.parent - contains a reference to the window object that contains the frame

window.screen - contains information about the screen on which the window is displayed like height, width, availHeight, availWidth and colorDepth.

window.self - A reference to the current window.

window.top - A reference to the top-level window when working with frames.

Methods GET vs. POST in HTML forms.

2010-02-08T05:42:00.000-08:00

Encoding form data into URL is needed by the GET method. The form data is to be appeared within the message body , by the POST method. By specification, GET is used basically for retrieving data where as POST is used for data storing, data updating, ordering a product or even e-mailing.

JavaScript - Methods GET vs. POST in HTML forms

The GET method in the HTML forms passes the form values by setting the URL.

Eg: If you type the word ‘Hello’ in Google Search, it sets the following URL:

http://www.google.co.in/search?hl=en&q=hello&btnG=Search&meta=&aq=f&oq=

The POST method sends the data to the server without setting the URL:

Eg:
-----------------------------97891525516423
Content-Disposition: form-data; name="username"

aaaa
-----------------------------97891525516423
Content-Disposition: form-data; name="password"

bbbbb12345
-----------------------------97891525516423
Content-Disposition: form-data; name="submit"

Submit
-----------------------------97891525516423--

JavaScript - What does the EnableViewStateMac setting in an aspx page do? -

Opening Browser Windows using JavaScript

newWindowObj = window.open("URL", "WindowName", " EnableViewStateMac setting is a security measure in ASP.Net. It ensures the view state for a page not to tamper. To to so “ EnableViewStateMac=true “is used. ASP.net detects the change in the value of view state sent to the browser when Postback action takes place and raises an error – “Validation of view state MAC failed”.

JavaScript - What does the EnableViewStateMac setting in an aspx page do?

EnableViewStateMac is a security measure used by ASP.NET in order to ensure that the viewstate for a page has not been tampered with.

ASP.NET raises an error (Validation of viewstate MAC failed) if it detects that there has been a change in the value of viewstate that was sent to the browser.

JavaScript - What are windows object and navigator object in JavaScript? -

Windows object is top level object in Java script. It contains several other objects such as, document, history, location, name, menu bar etc., in itself. Window object is the global object for Java script that is written at client-side.

Information pertaining to the client browser and system is returned by the navigator object of JavaScript. Navigator object is the top level object for all users.

JavaScript - What are windows object and navigator object in JavaScript?

The details of the client browser can be obtained sing JavaScript. Details such as client name, version, codename and the platform can be obtained.
navigator.appName - Gives the name of the browser
navigator.appVersion - Gives the browser version
navigator.appCodeName - Gives the browser codename
navigator.platform - Gives the platform on which the browser is running
The JavaScript Window Object is the top level JavaScript object which corresponds to the web browser window.

feature, feature, feature ... ");
features - A comma separated list of features that allow you to customize the appearance of the window

How to detect the operating system on the client machine in JavaScript?

The navigator.appVersion string should be used to find the name of the operating system on the client machine. The following code snippet returns the appropriate Operating systems.

var OSName="Unknown OS";
if (navigator.appVersion.indexOf("Win")!=-1) OSName="Windows";
if (navigator.appVersion.indexOf("Mac")!=-1) OSName="MacOS";
if (navigator.appVersion.indexOf("X11")!=-1) OSName="UNIX";
if (navigator.appVersion.indexOf("Linux")!=-1) OSName="Linux";

How to detect the operating system on the client machine in JavaScript?

navigator.platform returns the platform on which the browser is running

JavaScript vs. Jscript

2010-02-08T05:41:00.001-08:00

JavaScript is a scripting language developed by Netscape Communications.
The Netscape Navigator interprets JavaScript embedded into Web pages.
JavaScript is used for developing web applications.
It is not dependent on Sun Microsystem's Java language.

JScript
Microsoft JScript is an open implementation of Netscape's JavaScript.
JScript is a scripting language designed to create active online content. ActiveX controls, Java programs, etc can be linked and automated in the web pages using JScript.

What is the difference between Client side JavaScript and Server side JavaScript.

Client side java script comprises the basic language and predefined objects which are relevant to running java script in a browser. The client side java script is embedded directly by in the HTML pages. This script is interpreted by the browser at run time.

Server side java script also resembles like client side java script. It has relevant java script which is to run in a server. The server side java scripts are deployed only after compilation.

What is the difference between Client side JavaScript and Server side tJavaScript?

Client-Side JavaScript (CSJS)
It is JavaScript that enables the enables web pages on browsers to run active online content.

Server-Side JavaScript (SSJS)
It is JavaScript that enables back-end access to databases, file systems, and servers

Where are cookies actually stored on the hard disk?

The storage of cookies on the hard disk depends on OS and the browser. The Netscape navigator on Windows, the file cookies.txt contains all the cookies. The path is :

c:\Program Files\Netscape\Users\username\cookies.txt

The Internet Explorer stores the cookies on a file by name username@website.txt is

c:\Windows\Cookies\username@Website.txt

JavaScript - Where are cookies actually stored on the hard disk?

This depends on the user's browser and OS.

In the case of Netscape on Windows OS, its stored in cookies.txt

In IE, each cookie is stored in a file and has is named as username@website.txt.

JavaScript - What is the difference between a web-garden and a web-farm? -

Web garden is a web hosting system. It is a setup of multi processors in single server.

Web farm is a web hosting system. It is a multi-server scenario.

What is the difference between a web-garden and a web-farm?

The term ‘Web Farm’ indicates a business that performs Web site hosting on multiple servers.

The term ‘Web Garden’ means a multi-processor machine

What is the difference between SessionState and ViewState?

The values of controls of a particular page of the client browser is persisted by ViewState at the time of post back operation is done. If the user requests another page, the data of previous page is no longer available.

The data of a particular server persists in the server by SessionState. The availability of the user data is up to the completion of a session or closure of the browser.

A ViewState is a state of a page within a browser wherein the values of controls persist when post back operation is done.
When another page is loaded, the previous page data is no longer available.

SessionState is the data of a user session and is maintained on the server side. This data available until user closes the browser or session time-outs.

How to Accessing Elements using javascript?

The elements of JavaScript are accessed by their names. By default the browser is accessed by the element ‘windows’ and the page by ‘document’. The corresponding element has user defined names for forms and its elements. For example

var passwd = windows.document.frmLogin.password.value;

assigns the value of the password field of the form fromLogin in the current document, where password is the name of the element and frmLogin is the name of the form. Like wise any form element is accessed.

How to Accessing Elements using javascript?

Following are some of the functions with which the elements can be retrieved:

getElementById()
getElementByName()
getElementByValue()
getElementByTag()

What is the difference between undefined value and null value?

Undefined value: A value that is not defined and has no keyword is known as undefined value. For example in the declaration, int number; the number has undefined value.

Null value: A value that is explicitly specified by the key word ‘null’ is known as null value. For example in the declaration, String str=null; the str has a null value. The keyword ‘null’ is used here.

null value has keyword called ‘null’. That is not the case with undefined.

typeof undefined variable or property returns undefined whereas
typeof null value returns object.

How to set the cursor to wait in JavaScript?

The cursor can set to wait in JavaScript by using the property ‘cursor’ property. The following example illustrates the usage.

window.document.body.style.cursor = "wait"; // sets the cursor shape to hour-glass.

How to set the cursor to wait in JavaScript?

A moue over this yellow patch will show you the wait cursor.

What is decodeURI(), encodeURI() in JavaScript?

To send the characters that can not be specified in a URL should be converted into their equivalent hex encoding. To perform this task the methods encodeURI() and decodeURI() are used.

For example, the following code snippet performs the encoding of URL:

What is decodeURI(), encodeURI() in JavaScript?

These functions are used to encode and decode the URIs.

Eg:
String: Career Ride

Operation: encodeURI()
Output: Career%20Ride

Operation: decodeURI()
Output: Career Ride

What is JavaScript?

2010-02-08T05:41:00.000-08:00

JavaScript is a scripting language most often used for client-side web development.

What boolean operators does JavaScript support?

Answer
==
!=
<
>
<=
>=

Is a javascript script faster than an ASP script?

Answer
JSP is faster then ASP as the script is run on the client side. Only the computation is done on the server side.

What is == operator ?

Answer
The ‘==’ operator is a boolean comparison operator that returns true if the variables on its both sides are compared equal else it returns false.

What is negative infinity?

Answer
It’s a number that is obtained by dividing a negative number by zero. (in JSP)

What’s relationship between JavaScript and ECMAScript?

Answer
JavaScript is a scripting language most often used for client-side web development. It was the originating dialect of the ECMAScript standard. ECMAScript and LiveScript are other names for JavaScript. The current JavaScript that is supported in browsers is ECMAScript revision 3.

What does isNaN function do?

Answer
The isNaN function determines if the value is a number or not and depending upon the result, it returns true or false.

How to read and write a file using javascript?

There are two ways to do it:

1. Using JavaScript extensions (runs from JavaScript Editor), or

2. Using a web page and ActiveX objects (Internet Explorer only)

In JavaScript Extensions, you can use
fh = fopen(getScriptPath(), 0); to open a file

Using ActiveX objects, following should be included in your code to read a file:

var fso = new ActiveXObject("Scripting.FileSystemObject");
var s = fso.OpenTextFile("C:\\example.txt", 1, true);

How do you create a new object in JavaScript?

In order to generate dynamic content, JSP provides for creating, modifying and interacting with Java objects. The implicit objects like page, config, request, etc are called so because their availability in the in JSP page is automatic.

Also, along with using constructor functions (e.g. var mything = new myObject();), you can use Object Initializers to create objects in JSP.
E.g:
var myCar = {color:"white",wheels:4,engine:{cylinders:4,size:2.2}};

How to create arrays in JavaScript?

Although you can create the arrays using ‘new’ (var myArray = new myArray[10];), it is recommended that you create it in the following way: var myArray = [];

You don't need to tell Javascript how many items to size the Array for. Javascript automatically increases the size of the Array as needed.

CSS Interview questions and answers

2010-02-08T05:39:00.000-08:00

Explain in brief about the term CSS.

A stylesheet language used to describe the presentation of a document written in a markup language. Cascading Style Sheets are a big breakthrough in Web design because they allow developers to control the style and layout of multiple Web pages all at once.

What are the various style sheets?

Inline, external, imported and embedded are the different types of style sheets.

What are style sheet properties?

CSS Background
CSS Text
CSS Font
CSS Border
CSS Outline
CSS Margin
CSS Padding
CSS List
CSS Table

List various font attributes used in style sheet.

font-style
font-variant
font-weight
font-size/line-height
font-family
caption
icon
menu
message-box
small-caption
status-bar

Explain inline, embedded and external style sheets.

Inline
If only a small piece of code has to be styled then inline style sheets can be used.

Embedded
Embedded style sheets are put between the tags.

External
If you want to apply a style to all the pages within your website by changing just one style sheet, then external style sheets can be used.

Index tuning & database partitioning

2010-02-08T05:36:00.000-08:00

What is “Index Tuning Wizard”?

Index Tuning Wizard is a software application that identifies tables which have inefficient indexes. It makes recommendations on how indexes should be built on a database to optimize performance. The recommendations are based on T-SQL commands that the wizard analyzes.

List out what Index Tuning Wizard can do.

It identifies tables in need of an index change
Implements recommendations
Determines how a proposed change might affect performance
Has the capability to make indexes change immediately and schedule them
Helps to tune indexes.

Explain how partitioning an important part of database optimization is.

Partitioning distributes database tables over different database which may reside on a different server. Vertical portioning helps to fit more rows on a database page to improve data access performance. Partitioning helps to do multiple tasks simultaneously. It increases performance. It helps to manage data.

SQL Server distributed queries

2010-02-08T05:35:00.002-08:00

SQL Server distributed queries -

Answer
Distributed queries access data from multiple heterogeneous sources. These data sources may or may not be stored on the same computer. Distributed queries are most useful when there are multiple databases of varied nature. Hence, distributed queries can be executed over these databases in a secure manner.

Describe how Linked server is used to excess external data.

Answer
A linked server can be considered as another SQL server database running elsewhere. It can be a OLEDB or ODBC data source. They help in addressing distributed queries.

OPENQUERY function is used for such purposes. This function I is used to execute the specified query on the linked sever. OPENQUERY can be referenced in from the FROM clause just like a table name.

Example:
SELECT * FROM OPENQUERY(OracleSvr, 'SELECT name, id FROM joe.titles')

Describe how OPENQUERY function is used to excess external data.

Answer
OPENQUERY is used to execute the specified query on the linked sever.

OPENQUERY can be referenced in from the FROM clause just like a table name.

Syntax:

OPENQUERY ( linked_server ,'query' )

OPENQUERY does not accept variables for its arguments.

Example:
SELECT * FROM OPENQUERY (OracleSvr, 'SELECT name, id FROM joe.titles')

Describe how OPENROWSET and OPENDATASOURCE function is used to access external data.

OPENROWSET: Includes all connection information that is required to access remote data from an OLE DB data source. It can be references from a FROM clause and is used to access the tables on a linked server. It can also be referenced as a target table of INSERT, DELETE, and UPDATE statements.

Syntax:
OPENROWSET
( { 'provider_name' , { 'datasource' ; 'user_id' ; 'password'
| 'provider_string' }
, { [ catalog. ] [ schema. ] object
| 'query'
}
| BULK 'data_file' ,
{ FORMATFILE = 'format_file_path' [ ]
| SINGLE_BLOB | SINGLE_CLOB | SINGLE_NCLOB }
} )

Example
SELECT * FROM OPENROWSET('SQLNCLI',Server=Brighton1;Trusted_Connection=yes;', 'SELECT sal, employee_name FROM Company.employee.ID')

OPENDATASOURCE: Provides ad hoc connection information without a linked server name.

Syntax:
OPENDATASOURCE ( provider_name, init_string )

Example: The example cretes a ad hoc connection to the payroll instance of a SQL server in US. It queries the Company.HumanResources.Employee table.

SELECT * FROM OPENDATASOURCE('SQLNCLI', 'Data Source=US\Payroll;Integrated Security=SSPI') . Company.HumanResources.Employee

SQL Server Distributed Queries

Distributed queries can access data from different data sources.
These sources can reside on the same server or a different server.
Theycan querymultiple databases. .

SQL Server method to insert data interview questions

2010-02-08T05:35:00.001-08:00

Brief about Insert Statement with an example.

Answer
INSERT: The Insert statement is used to insert values as rows in a table.

Syntax:
INSERT INTO Table_name values (value1, value2,…);
INSERT INTO Table_name (column1, colum2…) values (value1, value2,…);

Example
A table customer has fields customer id, customer name, customer salary.
INSERT INTO customer (1,John,20000);

Brief about Select….into statement with an example.

Answer
Select into is used to create back up copies of tables. It selects data from one table and inserts into another.

Syntax:
Select * INTO dest_table_name FROM source_table_name

Example: Select data from customer table into customer_backup
Select * INTO customer_backup FROM customer;

It can also be used with WHERE clause for a condition.
Select * INTO customer_backup FROM customer WHERE cust_salary > 1000;

Brief about Bulk copy with an example.

Answer
Bulk copy utility of SQL allows data to be copied from one data file to another. The data is first exported from the source data file and then imported into the SQL server using the bcp command. It can also be used to transfer data from a table to a file.

Describe how bcp command prompt utility is used to import and export data.

Answer
The bcp utility is accessed from the command prompt.

Syntax:
bcp {dbtable | query} {in | out | queryout | format} datafile [-n native type] [-c character type] [-S server name] [-U username] [-P password] [-T trusted connection]

It starts with specifying the database or object name. In and out means whether the data needs to be copied into or out of the database. Hence in will be used for importing data while out will be used to export data. Remaining arguments are the basic command line arguments.

Example1: import data of Company database to the employee table
bcp Company.dbo.employee in c:\temp\employee.bcp -c -Sstevenw -Usa –P

Example2: Export data of Company database from the employee table
bcp Company.dbo.employee out c:\temp\employee.bcp

Describe how bulk insert statement is used to import data.

Answer
Bulk Insert is used to copy data from a file into a table or view in a format as specified by the user.

Syntax:
BULK INSERT
[ database_name . [ schema_name ] . | schema_name . ] [ table_name | view_name ]
FROM 'data_file'
[ WITH
(
[ [ , ] BATCHSIZE = batch_size ]
[ [ , ] CHECK_CONSTRAINTS ]
[ [ , ] CODEPAGE = { 'ACP' | 'OEM' | 'RAW' | 'code_page' } ]
[ [ , ] DATAFILETYPE =
{ 'char' | 'native'| 'widechar' | 'widenative' } ]
[ [ , ] FIELDTERMINATOR = 'field_terminator' ]
[ [ , ] FIRSTROW = first_row ]
[ [ , ] FIRE_TRIGGERS ]
[ [ , ] FORMATFILE = 'format_file_path' ]
[ [ , ] KEEPIDENTITY ]
[ [ , ] KEEPNULLS ]
[ [ , ] KILOBYTES_PER_BATCH = kilobytes_per_batch ]
[ [ , ] LASTROW = last_row ]
[ [ , ] MAXERRORS = max_errors ]
[ [ , ] ORDER ( { column [ ASC | DESC ] } [ ,...n ] ) ]
[ [ , ] ROWS_PER_BATCH = rows_per_batch ]
[ [ , ] ROWTERMINATOR = 'row_terminator' ]
[ [ , ] TABLOCK ]
[ [ , ] ERRORFILE = 'file_name' ]
)]

Example:
BULK INSERT target.txt FROM ‘C:\Dest.txt’ WITH ( FIELDTERMINATOR = ‘ ” , ” ‘)
The FIELDTERMINATOR argument allows you to specify the delimiter used to discern column values.

SQL Server cube operator interview questions

2010-02-08T05:35:00.000-08:00

Explain how to use Cube operator to summarize data.

Answer
A Cube operator summarizes data of group by. It helps in determining subtotals and grand totals.

Example: This will display a summary of employees with same first name.

Select first_name, last_name, AVG(salary) FROM employee GROUP BY first_name WITH CUBE