计算形状Shape(圆Circle，矩形Square ，正方形Rectangle)的面积、周长

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace _计算形状
{
class Program
{
static void Main(string[] args)
{
//作业：计算形状Shape(圆Circle，矩形Square ，正方形Rectangle)的面积、周长
Shape shape = new Square(5,7);//new Circle(5);
double area = shape.GetArea();
double perimeter = shape.GetPerimeter();
Console.WriteLine(area);
Console.WriteLine(perimeter);
Console.ReadKey();
}
}

public abstract class Shape
{
public abstract double GetArea();
public abstract double GetPerimeter();
}

public class Square : Shape
{
public double Height
{
get;
set;
}

public double Width
{
get;
set;
}

public Square(double height, double width)
{
this.Height = height;
this.Width = width;
}

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

public override double GetPerimeter()
{
return (this.Height + this.Width) * 2;
}
}

public class Circle : Shape
{
public double R
{
get;
set;
}
public Circle(double r)
{
this.R = r;
}

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

public override double GetPerimeter()
{
return 2 * Math.PI * this.R;
}
}
}