C#使用虚方法求一个圆的面积和周长

//定义一个父类的虚方法
public abstract class Person
{

  public abstract double GetArea();
  public abstract double GetPrimeter();

}
//继承虚方法父类的子类
public class Circle : Person
{
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 * R * R;
    }

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

//子类创建一个实例对象并传入一个构造函数对应的参数
Circle c = new Circle(5);
Console.WriteLine($"Circle Area{c.GetArea()},primeter{c.GetPrimeter()}");