【Refactoring】帮忙重构一个C#程序

悬赏园豆：50 [已关闭问题]

我有一个画图演示程序：在不同的表面上画不同的形状。

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表面：Surface(表面)、EtchASketch(浮雕表面)

形状：Shape(形状)、Ploygon(多边形)、Quadrilateral(四边形)、Parallelogram(平行四边形)、Rectangle(矩形)

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下面的代码，显然违反了OCP原则：

如果要添加一个新Surface的话，我必须要在所有的Shape里添加新方法！

我想请高手们看看，应该如何重构这段程序，以及说说为什么？

非常感谢！

    class Surface
    {
        public virtual void Draw(Shape shape)
        {
            shape.Draw(this);
        }
    }

    class EtchASketch : Surface
    {
        public override void Draw(Shape shape)
        {
            shape.Draw(this);
        }
    }

    class Shape
    {
        public virtual void Draw(Surface surface)
        {
            Console.WriteLine("A shape is drawn on the surface with ink.");
        }

        public virtual void Draw(EtchASketch etchASketch)
        {
            Console.WriteLine("The knobs are moved in attempt to draw the shape.");
        }
    }

    class Polygon : Shape
    {
        public override void Draw(Surface surface)
        {
            Console.WriteLine("A polygon is drawn on the surface with ink.");
        }

        public override void Draw(EtchASketch etchASketch)
        {
            Console.WriteLine("The knobs are moved in attempt to draw the polygon.");
        }
    }

    class Quadrilateral : Polygon
    {
        public override void Draw(Surface surface)
        {
            Console.WriteLine("A quadrilateral is drawn on the surface with ink.");
        }

        public override void Draw(EtchASketch etchASketch)
        {
            Console.WriteLine("The knobs are moved in attempt to draw the quadrilateral.");
        }
    }

    class Parallelogram : Quadrilateral
    {
        public override void Draw(Surface surface)
        {
            Console.WriteLine("A parallelogram is drawn on the surface with ink.");
        }

        public override void Draw(EtchASketch etchASketch)
        {
            Console.WriteLine("The knobs are moved in attempt to draw the parallelogram.");
        }
    }

     class Rectangle : Parallelogram
    {
        public override void Draw(Surface surface)
        {
            Console.WriteLine("A rectangle is drawn on the surface with ink.");
        }

        public override void Draw(EtchASketch etchASketch)
        {
            Console.WriteLine("The knobs are moved in attempt to draw the rectangle.");
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            Surface surface = new Surface();
            Surface etchASketch = new EtchASketch();

            var shapes = new List<Shape>
                             {
                                 new Shape(),
                                 new Polygon(),
                                 new Quadrilateral(),
                                 new Parallelogram(),
                                 new Rectangle()
                             };

            foreach (Shape shape in shapes)
            {
                surface.Draw(shape);
                etchASketch.Draw(shape);
            }

            Console.ReadLine();
        }
    }