Explain the protocols a .Net Web Service uses.

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.