关于#c##的问题，请各位专家解答！

题主要的代码如下

using System;
using System.Reflection;
using System.Linq;
namespace ConsoleApp1
{
    class Circle
    {
        public const double PI = 3.14;
        private double radius;
        public double Radius { get { return radius; } set { radius = value > 0 ? value : 0; } }
        public double Area()
        {
            return PI * radius * radius;
        }
        public double Circum()
        {
            return 2 * PI * radius;
        }
    }
    class Demo
    {
        public static void Main()
        {
            var c1 = new Circle() { Radius = 4.7 };
            Console.WriteLine("面积：" + c1.Area());
            Console.WriteLine("周长：" + c1.Circum());

            var c2 = new Circle() { Radius = 3.6 };
            Console.WriteLine("面积：" + c2.Area());
            Console.WriteLine("周长：" + c2.Circum());

            Console.ReadKey();
        }
    }
}

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