I started developing a Silverlight (SL) 4 application hosted in an ASP.NET site using Visual Studio 2010. Now I want to change it so that the SL application runs out of browser as if I had not chosen to host it in a web site when I created the SL project.

First, I went to the properties of the web application and removed the SL project from the “Silverlight Applications” tab. Then, I went to the properties of the SL project and made sure the “Out-of-browser Application” option was chosen on the “Debug” tab with the SL project selected in the drop list. Finally, I made sure that the SL project was set as the “StartUp” project for the solution. The solution builds successfully however when I try to run I get the following message in an error dialog:

Unable to determine the URL to the Xap file from web [web project name].

I'm assuming this is happening because the SL project is trying to copy the Xap file to the ClientBin folder of the web site. Obviously, the SL and web projects are still linked in some way despite my attempt to unlink the two. I have examined each project file in notepad to find any reference between them with no luck. What’s more frustrating is that I can achieve my desired result by creating a new SL application and un-checking the “Host the Silverlight application in a new or existing Web site in the solution” option.

I know I could start my project over from scratch to solve this problem however I’m really curious as to what is causing this error. A Google search yielded no results.