chronoseraph wrote:1.What is the difference between these two?
One belongs to the Windows API and the other is the MFC version.
chronoseraph wrote:2.Which verision is used under what situation?( an example would be nice)
If you're using MFC, you might as well use the MFC version... it's usually easier to use when you're in that context anyway.
chronoseraph wrote:3.For the CWnd class verision, that is the hWnd send? ( does it default to the hWnd of the object that sends the message?)
It uses the hwnd that corresponds to the particular cwnd object. If you don't know the difference between hwnd and cwnd, that's a whole-nother bag-o-worms.
Hope that helps a bit.