判断素数（C#）

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来源：北大青鸟C#作业题

描述：判断用户输入一个正整数是否是素数。

工具：Visual Studio 2005  （控制台程序）

Source:

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

namespace P52_1
{
    class Program
    {
        static void Main(string[] args)
        {
            Cal a = new Cal();
            a.sushu();
        }
    }
    class Cal
    {
        private int c=0;
        string s;

        public int C
        {
            get
            {
                return c;
            }
            set
            {
                if (value <= 0)
                {
                    Console.WriteLine("请输入正数！");
                    return;
                }
                c = value;
            }
        }
        public void sushu()
        {
            Console.WriteLine("请输入一个正数：");
            do
            {
                s = Console.ReadLine();
                try
                {
                    C = Int32.Parse(s);
                }
                catch (Exception e)
                {
                    Console.WriteLine("请输入数字！");
                }
            } while (c <= 0);

            for (int i = 2; i < C; i++)
            {
                if (C % i == 0)
                {
                    Console.WriteLine("您输入的正数{0}不是素数，第一个整除的数是{1}", C, i);
                    return;
                }
            }
            Console.WriteLine("您输入的正数{0}是素数。", C);

        }
    }
}