本课我们来讲一下，如何利用C#进行加密，在类中的main方法中， 首先输出提示即“请输入四位整数”，接下来我们将输入的数字 存入到变量i中，再将变量i进行转换，即分别进行运算，运算后 存储到变量first、seconc、third、forth等四个变量中，然后在 控制台上输出，所有变量的值的组合连接，即

        Console.WriteLine("请输入四位整数：");
        int i=int.Parse(Console.ReadLine());

        int first = i/1000;
        int second = (i/100)%10;
        int third = (i/10)%10;
        int forth = i%10;

        Console.WriteLine(first+" "+second+" "+third+" "+forth);

第一阶段完成之后，接下来，分别对四个变量进行 二次运算，再输出

        first = (first+7)%10;
        second =(second+7)%10;
        third = (third+7)%10;
        forth = (forth+7)%10;
        int temp=third;
        third=first ;
        first = temp;

        temp= forth;
        forth= second;
        second = temp;

        int pass = first*1000+second*100+third*10+forth;

        Console.WriteLine("Now is "+pass);

        Thread.Sleep(5000);

全部代码如下：

using System;
using System.Threading;

class My303
{
    static void Main()
    {
        Console.WriteLine("请输入四位整数：");
        int i=int.Parse(Console.ReadLine());

        int first = i/1000;
        int second = (i/100)%10;
        int third = (i/10)%10;
        int forth = i%10;

        Console.WriteLine(first+" "+second+" "+third+" "+forth);

        first = (first+7)%10;
        second =(second+7)%10;
        third = (third+7)%10;
        forth = (forth+7)%10;

        int temp=third;
        third=first ;
        first = temp;

        temp= forth;
        forth= second;
        second = temp;

        int pass = first*1000+second*100+third*10+forth;

        Console.WriteLine("Now is "+pass);

        Thread.Sleep(5000);
    }
}