c# 验证码

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

namespace 验证码字符串做法
{
    class Program
    {
        static void Main(string[] args)
        {
            //定义一组字符串 验证码需要26个英文大小写和0~9的数字
            string[] s= new string[62]
            {"0","1","2","3","4","5","6","7","8","9",
                "a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s",
             "t","u","v","w","x","y","z",
                "A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q",
            "R","S","T","U","V","W","X","Y","Z"
            };
            string a="";//定义一个a的字符变量，值为空
            Random ran = new Random();//初始随机数
            for (int i = 0; i < 4;i++ )//验证码需要四个字符串，需要循环四次，每次随机一个字符串连成验证码
            {
                int suijishu = ran.Next(62);//数组里有62个字符串，创建62以内的随机数，用来随机数组内字符串的索引
                a+= s[suijishu];//将随机产生的四个字符连成一个字符串表示验证码
            }
            Console.WriteLine("验证码："+a);
            string b = a.ToUpper();//后台执行把输出的字符串全部转换为大写
            Console.Write("请输入验证码：");
            string r = Console.ReadLine();
            string q = r.ToUpper();//将用户输入的字符串全部转换为大写，以便与输出的字符串相比较
            if (q == b)//如果用户输入的和电脑输出的相同，则验证成功
            {
                Console.WriteLine("验证成功！");
            }
            else//如果不一样，则输入错误，外部也可以加个无限循环，当输入错误时重新输入，成功时if下面加break跳出
            {
                Console.WriteLine("输入错误！");
            }
            


            Console.ReadLine();
        }
    }
}