禁止用户关闭操作系统

private const int WM_QUERYENDSESSION=0x0011;
  protected override void WndProc(ref Message m)  
   {
        int i=0;
        switch(m.Msg)
        {
             case WM_QUERYENDSESSION:
               m.Result=(IntPtr)i;
               break;
             default:
               base.WndProc(ref m);
               break;
        }
    
   }