Question: When running a web application project, at seemingly random times a page may fail with a CS0433 error: type exists in multiple DLL's. The DLL's are all generated DLL's residing in the "Temporary ASP.NET Files" directory.

Answer: 
None of these answers worked for me, however I did fix the problem. Since I was using VS's Publish function to deploy the web application, I selected the option to **delete all existing files prior to publish** in the Publish Web wizard. This forced a clean copy of the application and everything worked fine from there.

This solution might be helpful if your local debugging copy works fine but published system isn't. Also great if you don't want to take the time to track down individual dlls to delete and don't mind the production files being deleted first.
Got this problem when put a part of an aspx page into the separate user control. On my machine everything was fine, on the server got an error.

**Renamed the problem class and file.**

<http://support.microsoft.com/kb/919284> Method 2: Reorder the folders in the application is writing about possible circular references