How to resolve VS2010 Windows Form Designer issue (base class could not be loaded)

Question

I have recently been getting an error in the Windows Forms designer of VS2010SP1 when using inherited UserControls.

The error is

The designer

Answer 1

I also have found that when you are trying to design a form that may have referenced libraries that are already in use, then it fails to design.

I often run several Visual Studio instances. If I leave an instance of VS running a program in debug mode, and that program shares a library with the instance of Visual Studio in which I am trying to design, then I run into this problem. It also can be as simple as the DLL that the designer references is in use.

Once you close the program that is locking those library files then the designed returns to normal.