通过实例说明树形控件的使用，并结合ControlBar使用-Through the examples of the use of tree controls, combined with the use of ControlBar

MFC多文档界面中的treecontraobar的实现，演示了treebar和视图间通信的关系。-MFC multi-document interface treecontraobar implementation, demonstrates treebar and view the relationship between the communication.