Chapter 12 On to the client. This logic is more or less the same as with Windows authentication, as described in the recipe Tracking a user's identity - default Windows authentication, with two notable changes: we're using Forms authentication now, so we need to define that that is what the WebContext will use, in App.xaml . This is done in step 8. The other change can be found in step 7: instead of just loading the user, as we did with Windows authentication, we now need to log in by calling the Login method on our authentication service. This will execute the server-side login method we just implemented, and the logged-in Employee will be loaded in our context when this method is completed and the credentials are valid. See also For more on authentication, have a look at the Tracking a user's identity ­ default Windows authentication and Integrating Windows Identity Foundation with WCF RIA Services recipes. For more advanced recipes on WCF RIA Services, have a look at the rest of this chapter. Integrating Windows Identity Foundation with WCF RIA Services Applies to Silverlight 4, 5 Besides using Windows and Forms authentication, there's another way to authenticate/authorize a user with WCF RIA Services: through Windows Identity Foundation (WIF). This consists of a set of classes with which you can build identity-aware applications. It allows us to externalize authentication and authorization: the application relies on an identity provider for this.