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

If you have Visual Nunit, it must be locking dll file.

1. Close VS
2. Go to taks manager , kill the Visual Nunit process
3. Now open VS and build the project