Скриншот с WPF WebBrowser

public static string GetThumbnailImage(WebBrowser CurrentBrowser)
{
    Guid guid = Guid.NewGuid();
    string ThumbnailPath =  guid.ToString() + ".png";
    Image imgScreen = new Image();
    imgScreen.Width = 120;
    imgScreen.Height = 100;
    imgScreen.Source = new DrawingImage(VisualTreeHelper.GetDrawing(CurrentBrowser));
    FileStream stream = new FileStream(ThumbnailPath, FileMode.Create);
    DrawingVisual vis = new DrawingVisual();
    DrawingContext cont = vis.RenderOpen();
    cont.DrawImage(imgScreen.Source, new Rect(new Size(120d, 100d)));
    cont.Close();
    RenderTargetBitmap rtb = new RenderTargetBitmap((int)imgScreen.Width,
    (int)imgScreen.Height, 96d, 96d, PixelFormats.Default);
    rtb.Render(vis);
    PngBitmapEncoder encoder = new PngBitmapEncoder();
    encoder.Frames.Add(BitmapFrame.Create(rtb));
    encoder.Save(stream);
    stream.Close();
    return ThumbnailPath;
}