In this article, Mahesh Sabnis demonstrates how to make a Web request to an external service using the Network Authentication feature.
When you develop Line-of-Business (LOB) applications using Silverlight, many a times you need to make a call to a WCF service and retrieve data from it. Now this service can be a WCF REST service and to make call to this service; the credential information required to send to the service might be different from the credentials of the logged in user. So in this case, to send request to the WCF service from Silverlight 4.0 client, you need to use the ‘WebClient’ class.