编程时碰到的一个怪问题

BOOL  CMainFrame::PreCreateWindow(CREATESTRUCT&  cs)  
{  
           if(  !CFrameWnd::PreCreateWindow(cs)  )  
                       return  FALSE;  
           //  TODO:  Modify  the  Window  class  or  styles  here  by  modifying  
           //    the  CREATESTRUCT  cs  
           cs.cx  =  400;  
           cs.cy  =  300;  
           cs.lpszName  ="HZY";  
           //cs.style  &=  ~FWS_ADDTOTITLE;  
           cs.style  =  WS_OVERLAPPEDWINDOW;  
           WNDCLASS  wndclass;  
             
           wndclass.cbClsExtra  =  0;  
           wndclass.cbWndExtra  =  0;  
           wndclass.hbrBackground  =  (HBRUSH)GetStockObject(BLACK_BRUSH);  
           wndclass.hCursor                  =  LoadCursor(NULL,IDC_HELP);  
           wndclass.hIcon                              =  LoadIcon(NULL,IDI_ERROR);  
           wndclass.hInstance                  =  AfxGetInstanceHandle();  
           wndclass.lpfnWndProc      =  ::DefWindowProc;  
           wndclass.lpszClassName  =  "huangzhiyang";  
           wndclass.lpszMenuName    =  NULL;  
           wndclass.style                          =  CS_HREDRAW    ¦  CS_VREDRAW;  
 
 
       if(!RegisterClass(&wndclass))  
           {  
                       MessageBox("hahaha");  
           }  
           cs.lpszClass  =  "huangzhiyang";  
             
           return  TRUE;  
}  
 
这里面用了  if(!RegisterClass(&wndclass))  会跳出对话框显示hahaha  
但是改成　    if(RegisterClass(&wndclass))后还是会跳出该对话框，  
不知道是什么原因？