A error message on MFC - a required resource was unavailable

CPaintDC dc(this); //may curse "a required resource was unavailable" error message// device context for painting

宣告CPaintDC在不是OnPaint的地方
所造成的問題

根據MFC - 繪圖得知CPaintDC要放在OnPaint的地方
其他的地方 可以用CClientDC來取代