That could be. I've never looked at WF frameworks. But I *have* attended *lots* of .NET conferences and several MVP Summits at Microsoft and never heard anyone say you should subclass everything. In fact, I rarely heard that you should subclass. (Note: Interfaces are a different story)

>I'm not sure the case is as clear cut when it comes to WinForms? Firstly it is easier to implement than in WPF (and there is no inherent downside). Surely most WF frameworks rely on sub-classed controls to simplify databinding, error validation etc.....