c#之抽象类源代码

using System;
abstract class Figure
{
    public Figure(double x, double y)
    {
        this.x = x;
        this.y = y;
    }
    public abstract void Area();
    protected double x = 0;
    protected double y = 0;
}
class Square:Figure
{
    public Square(double x, double y):base(x, y)
    {
        Console.WriteLine("constructor of Square has been called!");
    }
    public override void Area()
    {
        Console.WriteLine("square area:" + x * y);
    }
}
class Circle:Figure
{
    public Circle(double x):base(x, x)
    {
        Console.WriteLine("constructor of Circle has been called!");
    }
    public override void Area()
    {
        Console.WriteLine("circle area: " + Math.PI * x * x);
    }
}
class CRunMain
{
    public static void Main()
    {
        Figure objA = new Square(10, 20);
        Figure objB = new Circle(20);
        objA.Area();
        objB.Area();
    }
}