C#_OOP_2a_Circle.cs

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

namespace OOPGeometry2
{
    class Circle : Figure
    {
        private double r;

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

        public Circle(double r)
            : base("Circle")
        {
            this.r = r;
        }

        public override double CalculateSurface()
        {
            return r * r * Math.PI;
        }
    }
}