>CBrush* oldBrush = dc.SelectStockObject(NULL_BRUSH);
>
>i got this error message when compiling
>
>Cannot conver CGdiObject to CBrush

Ok, change it to
CGdiObject* oldBrush = dc.SelectStockObject(NULL_BRUSH);
or
CBrush* oldBrush = (CBrush*)dc.SelectStockObject(NULL_BRUSH);