Problem running silverlight app in VS 2010 beta

In Visual Studio 2010 Beta 2 I created a new navigation Silverlight application. Without changing anything I hit F5 to run the application. It c开发者_如何学Pythonomes up with the following error: ‘Unhandled error in Silverlight Application Code: 2104’. Does anyone know how I can fix this issue?

I’ve just worked out what the problem was: I didn’t realise the Silverlight xap wasn’t built automatically when you hit F5 in Visual Studio, so, the web application was looking for a file that wasn’t there. All I had to do to fix the problem was to build the Silverlight project