In this article written for the Visual Studio Magazine, Kathleen Dollard explores the nuances of using WCF Services with Silverlight.
For most data, you'll use a Windows Communication Foundation (WCF) service. Silverlight and WCF are an interesting combination because they force programmers who've avoided WCF into suddenly using it, and simultaneously force an asynchronous data model. WCF is an enormous topic and a key area of .NET specialization. If you're running a heavily loaded server or designing complex business-to-business service interactions, you may wish to bring in a specialist. But WCF as a data-access mechanism for Silverlight in less-extreme situations is not difficult. I'll show you how to use WCF, and I'll cover debugging a little later in this article.