C＃复制粘贴图像区域到另一个图像

public static void CopyRegionIntoImage(Bitmap srcBitmap, Rectangle srcRegion,ref Bitmap destBitmap, Rectangle destRegion) 
    { 
     using (Graphics grD = Graphics.FromImage(destBitmap))    
     { 
      grD.DrawImage(srcBitmap, destRegion, srcRegion, GraphicsUnit.Pixel);     
     } 
    }