WCF services can be accessed by a variety of clients, and this post will talk briefly about accessing services from Silverlight. The same familiar programming model applies to Silverlight as any WCF client application.

The first step in developing Silverlight clients is to set up a development environment. If you already have Visual Studio 2008 SP1 on the box, all that is needed is to install the Microsoft Silverlight Tools for Visual Studio 2008, available on this page (among other resources). The package will install the Silverlight runtime (the piece required to run Silverlight apps in the browser), the Silverlight SDK (the libraries and tools needed to build apps), and the Visual Studio project templates and other supporting features.

To create your first WCF service and Silverlight client combination, follow the steps in this set of documentation topics. Note that only certain WCF bindings and features are supported in Silverlight, and you can consult this page for a full description.

A common pitfall for developers new to Silverlight is the cross-domain restriction in the networking stack. For security reasons, if the WCF service and Silverlight client live on different domains (for example http://fabrikam.com/service.svc and http://contoso.com/mysilverlightcontrol.html), the service domain needs to use a cross-domain policy file to explicitly opt in to be accessible by Silverlight clients (for example http://fabrikam.com/clientaccesspolicy.xml). For a description of the cross-domain restriction, see this topic. For an example cross-domain policy file, see this topic.

If you get stuck at any point in the process so far, this article explains how to easily debug the service-client pair.

After you have built your first Silverlight WCF solution, you can move on to some advanced scenarios. Here is a list of areas you may wish to explore:

• Duplex communication - WCF services can "push" data to Silverlight clients, without the user having to manually poll the service. This is also known as a "notification" communication pattern, as opposed to a "request/reply" pattern. This topic walks you through implementing this scenario. The programming model for duplex services is rather complex, so our team has implemented a code sample which hides away some of that complexity. Check out the "Duplex Services" section of this blog post for more information and a link to the sample. In the next version of Silverlight, a greatly simplified duplex programming model is being considered.
• REST services - this class of web services uses light-weight wire formats (such as plain XML or JSON) and clear URI conventions for a simple experience consuming services. This set of topics highlights how WCF in Silverlight can be used to access REST services.

Here are some good resources for follow-up:

• Silverlight web services documentation - content from this resource was already referred to multiple times
• Silverlight web services team blog
• Silverlight web services code samples

Going forward, content from the Silverlight web services team blog (linked above) will be syndicated over here at the .NET Endpoint blog. Please keep an eye out for exciting new content coming up over the next month.

Yavor Georgiev
Program Manager
Connected Framework Team