DrawingVisual不起作用

Question

我想创建一个绘图应用程序。我有三个主要班级。

形状类中的方法：

 public DrawingVisual Paint()
    {
        DrawingVisual dv = new DrawingVisual();
        using (DrawingContext dc = dv.RenderOpen())
        {
            Pen pen = new Pen(new SolidColorBrush(Color), Stroke);
            dc.DrawRectangle(null, pen, new Rect(0, 0, Width, Height));
        }

        return dv;
    }

另一个类中的渲染方法：

 private void Render(DrawingContext dc)
    {
        System.Windows.Media.Pen pen = new System.Windows.Media.Pen(System.Windows.Media.Brushes.Black, 2);
        // Shape is my basic class for all my shapes
        foreach (Shape shape in shapes)
        {
            DrawingVisual visual = shape.Paint();

            VisualBrush brush = new VisualBrush(visual);
            dc.DrawRectangle(brush, null, new Rect(shape.X, shape.Y, shape.Width, shape.Height));
        }
    }

和OnRender方法：

protected override void OnRender(DrawingContext dc)
    {
        base.OnRender(dc);
        dc.DrawImage(image, new Rect(0, 0, image.Width, image.Height));

        System.Windows.Media.Pen pen = new System.Windows.Media.Pen(System.Windows.Media.Brushes.Black, 2);
        Render(dc);
    }

但是DrawingVisual类不起作用。你能帮我吗？