CDC使用下面三行可以省略掉????
CDC析构的时候会自动调用DeleteDC函数，所以没必要手动DeleteDC
CDC* pdc = GetDC();
CDC dc;
CBitmap bitmap;
bitmap.LoadBitmap(IDB_BITMAP1);
dc.CreateCompatibleDC(pdc);
dc.SelectObject(&bitmap);
BITMAP bit;
bitmap.GetObject(sizeof(bit),&bit);
pdc->BitBlt(0,0,bit.bmWidth,bit.bmHeight,&dc,0,0,SRCCOPY);
ReleaseDC(pdc);//下面三行可以省略掉?
dc.DeleteDC();
bitmap.DeleteObject();
