The located assembly's manifest definition does not match the assembly reference

Question

I am trying to run some unit tests in a C# Windows Forms application (Visual Studio 2005), and I get the following error:

System.IO.FileLoadException: Co

Answer 1

I just ran across this issue and the problem was I had an old copy of the .dll in my application debug directory. You might want to also check there (instead of the GAC) to see if you see it.