Using derived Class from CEdit in my DIalog

Question

I'm doing an application using MFC. I just made a class that is derived from CEdit so I could intercept OnChar() and do data validation. How do I substitute the edit control in my application with the derived one I made?

Answer 1

Do NOT use GetDlgItem!!

GetDlgItem() returns a CWnd-pointer and nothing else. This means you have a sliced CMyCustomEdit pointer. Sure, it works in all cases where your method sends a message to the underlying HWND. But that's just pure luck! You can read more about the problem here.

The right solution is to subclass your edit control using DDX_Control.