In a MVC2 project I moved a file from App_code to Content folder and compiled it. Then move it back again to App_Code and then changed its Build Action to "Compile". Now I get this error and I don't know how to fix this to make my program work again:
CS0433: The type 'Helper' exists in both 'c:\Users...\AppData\Local\Temp\Temporary ASP.NET Files\root\b00d4b7d\b2553f9c\App_Code.zowyklar.dll' and 'c:\Users...\AppData\Local\Temp\Temporary ASP.NET Files\root\b00d4b7d\b2553f9c\assembly\dl3\5c6d3537\19f85663_cde9cb01\MyProject.DLL'
Cleaning and Rebuilding doesn't solve the problem.
Try cleaning your solution and then try to rebuild. Visual Studio probably still has reference to the old dll after it created the new dll.