CTreeItem保存和获取数据

保存数据：

 std::string val = "test data";
 CString* pNodeData = new CString;
 *pNodeData = val.c_str();
 CTreeItem item;
 item.SetData((DWORD)pNodeData);

获取数据：

 DWORD data = item.GetData();
 CString *cstr = (CString*)data ;
 std::string result = cstr->GetBuffer();