我想生成一个MDI窗口的介面，但发现用VC实现起来很麻烦，要加很多很多的RUNTIME_CLASS，而且不能实现在主窗口中加入功能选项。就是说生成一个OUTLOOK的主窗口，在主窗口中再 加入多文档窗口（象OFFICE的多文档子窗口）。因此，写了这个CMDIChild的类。-I want to produce one MDI window lie between the surface, but discovers realizes with VC is very troublesome, must add very many very many RUNTIME_CLASS, moreover cannot realize in the host window joins the function option. Is says produces one OUTLOOK the main window, joins the multi- documents window again in the host window (looks like OFFICE the multi- articles window). Therefore, wrote this C$mDIChild kind.