C#实战-圆半径

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

namespace PI
{
    class Program
    {
        static void Main(string[] args)
        {
            const Double PI=3.1415926;
            Console.WriteLine("请输入圆的半径:");
            float r = Convert.ToInt32(Console.ReadLine());
            double s =PI * (r * r);
            Console.WriteLine("圆的半径是{0}，面积是：{1}",r,s.ToString("0.000"));//限制输出的位数
            Console.ReadKey();
        }
    }
}