...but I think all you guys are missing my point about the base WinForm controls classes

Geez, I guess I'm not "one of the guys" anymore. ;)

I agree 100% (not that you need any backing) - what you described is what I've been doing for years. I have one class file with all of my subclassed Winform controls. Some of them implement a generic binding interface. It is easier to maintain them in a single class. While I hate to say 'never', I can't think of a situation where I'd have a separate file [or project!] for each Winform control

Kevin