Window Destruction Sequence
The latest version of this topic can be found at Window Destruction Sequence.
In the MFC framework, when the user closes the frame window, the window's default OnClose handler calls DestroyWindow. The last member function called when the Windows window is destroyed is OnNcDestroy, which does some cleanup, calls the Default member function to perform Windows cleanup, and lastly calls the virtual member function PostNcDestroy. The CFrameWnd implementation of PostNcDestroy deletes the C++ window object.