C#使用多态求方形面积周长和圆的面积周长

  class class1
    {
        public static void Main(string[] args)
        {
            //使用多态求矩形面积与周长和圆的面积与周长
            Shape cl = new Circle();
            double clarea = cl.GetArea();
            double clpar = cl.GetPerimeter();
            Console.WriteLine("这个圆的面积是{0},周长是{1}", Math.Round(clarea, ), Math.Round(clpar, ));

            Shape sq = new Square(, );
            double sqarea = sq.GetArea();
            double sqpar = sq.GetPerimeter();
            Console.WriteLine("这个方形的面积是{0},周长是{1}", Math.Round(sqarea, ), Math.Round(sqpar, ));
            Console.ReadKey();
        }

    }

//声明一个抽像类
    public abstract class Shape
    {
        public abstract double GetArea();
        public abstract double GetPerimeter();
    }

class Circle:Shape
    {
        private double _r;

        public double R
        {
            get {
                return _r;
            }
            set {
                _r = value;
            }
        }

        public Circle(double r)
        {
            this.R = r;
        }
        public override double GetArea()
        {
            return Math.PI * this.R * this.R;
        }

        public override double GetPerimeter()
        {
            return  * Math.PI * this.R;
        }
    }

 class Square : Shape
    {
        private double _height;
        private double _width;

        public double Height
        {
            get
            {
                return _height;
            }
            set
            {
                _height = value;
            }
        }

        public double Width
        {
            get {
                return _width;
            }
            set {
                _width = value;
            }
        }
        public Square(double w, double h)
        {
            this.Height = h;
            this.Width = w;
        }
        public override double GetArea()
        {
            return this.Width * this.Height;
        }

        public override double GetPerimeter()
        {
            return (this.Width + this.Height) * ;
        }
    }