wpf 导出窗口截图

grid是窗口name,800，670是窗口宽度和高度

			RenderTargetBitmap rtbmp = new RenderTargetBitmap(800, 670, 96, 96, PixelFormats.Default);
            rtbmp.Render(grid);
            PngBitmapEncoder encode = new PngBitmapEncoder();
            encode.Frames.Add(BitmapFrame.Create(rtbmp));
            MemoryStream ms = new MemoryStream();
            encode.Save(ms);
            System.Drawing.Image MyImage = System.Drawing.Image.FromStream(ms);
            MyImage.Save(@"导出结果.PNG");