Theoretically you can derive from a Form, but is it something you should not do? I intuitively think so, but I’ve never heard of any rule like this.
I mean some conrete class that already derives from Form. For example, if I’ve got class MyForm : Form, the question is: can I derive from MyForm?
We’ve had success deriving a class from form and then deriving all of our forms in the project from it. It allows us to easily apply project-wide policies. All of our forms have a consistent look and feel. It also made it easy to have each form remember its size and location.