Debugging error “The Type 'xx' is defined in an assembly that is not referenced”

Question

The full error is as follows:

The type \'System.Windows.Forms.Control\' is defined in an assembly that is not referenced. You must add a reference to assembl

Answer 1

I had the same error.

The problem was that I used a reference to a project, which uses System.Windows.Forms inside.

The solution is to add a reference to System.Windows.Forms also in your project.