实现了一个CXMLFile类来操作XML文件，对应用程序设置选项的保存作了特别的接口支持，并实现了一个CPersistentTreeCtrl(一个可保存标签项的树控件)来演示CXMLFile类的用法。

-Implements a class to manipulate XML files CXMLFile, set the options for saving the application made a special interface support, and implementation of a CPersistentTreeCtrl (a label item to save the tree control) to demonstrate CXMLFile class usage.