自绘ComboBox，学自绘控件用的，希望对大家有用。-The CCstmComboBox class is derived from the MFC CComboBox class, and supports dialog data exchange and validation with DDX_CBString for CString and DDX_CBIndex for int variables like the ordinary CComboBox MFC class.

基本实现了在CListCtrl实现CCombobox的选择，对初学有意义-used for CListCtrl with CCombobox