MFC框架中的几个类的作用与相互关系，MFC框架窗口是如何产生和销毁的，对窗口类的PreCreateWidow和OnCreate两个函数的着重分析,Windows窗口与C++中的CWnd类的关系。-MFC in the fr a mework of the several types of roles and mutual relations, MFC fr a me window is how the generation and destruction of the window class