I really miss the option “set as start page” in Visual Studio Explorer for Silverlight Projects. If I have time in the next days (;-))Ii will write visual studio extension for that purpose. In fact it is not complicated. The app.xaml have a codebehind file ( app.xaml.vb or app.xaml.cs) which create a instance of the visible XAML. Btw that is the reason for changing xaml to usercontrol in B2.