学步园

将百分制转换为五分制，如果输入的百分制成绩超出0~100时，程序抛出异常。

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

namespace CSharp
{
    class Program
    {
        static void Main(string[] args)
        {
            while (true)
            {
                double num, num2;
                string s;
                Console.WriteLine("输入：x%,例如40%");
                s = Console.ReadLine();
                s = s.Substring(0, s.Length - 1);
                num = double.Parse(s);
                num2 = (5 * num) / 100;

                if (num > 100 || num < 0)
                {
                    try
                    {
                        throw new Exception();
                    }
                    catch (Exception ex) {
                        Console.WriteLine("error");
                    }
                }
                else
                    Console.WriteLine(num2 + "/5");
            }
            Console.ReadKey();
        }

    }
}