Unable to copy file reference.dll to bin/reference.dll. The process cannot access the file reference.dll because it is being used by another process

Question

For one of my ASP.NET 3.5 applications, every single time I try to build the web app, it throws the following build errors in Visual Studio 2008:

Error 16

Answer 1

This happens to me sometimes when using Visual Nunit for unit tests.

It seems the process 'VisualNunitRunner.exe' locks the .dll files in the destination directory.

I used Unlocker to find the process, kill it or unlock the files.