I had been trying to set up a development environment for Visual Studio so that instead of using the in-built Development Server (Cassini) I could use IIS. Since I had to develop on a Windows XP machine my first problem is that I could not create more that one Web Site under IIS 5.1 so I had to resort to using Virtual Directories for the applications (A Web app and a WCF app). This differed from the live setup where each was configured under its own web site and this is where my problems started. When I fired up the web application I was greeted with this error – The virtual path ‘/App_Resources/dev/mycontrol.ascx’ maps to another application which is not allowed.
For information on loading webforms and usercontrols from embedded resources take a look at http://www.codeproject.com/KB/aspnet/ASP2UserControlLibrary.aspx