True. We need to try to remember to enter the form code editor and comment out the Bentley Adapter class and inherit from System.Windows.Forms.Form class. Now we can use the form designer, makes changes and close the form designer. We can now uncomment the Bentley Adapter class and comment out System.Windows.Forms.Form class in the code editor.
We do not have this issue with the WPF designer. We could even use Blend.