要求：根据要求写代码

代码：

namespace 任务1
{
class Program
{

    static void Main(string[] args)
    {
        string flag ="";   //用于标识用户是否继续

        string userName = "";   //用户名
        string password = "";   //密码
        string cardNum = "";    //会员卡号

        bool isReg = false;
        bool isLogin = false;

        //获得随机数
        Random rd = new Random();
        int max = 9999;
        int min = 1000;


        do{
            Console.WriteLine(@"
*************欢迎进入魔法师幸运抽奖系统*************
                1、注册
                2、登录
                3、抽奖
*************************************************
");
            Console.Write("请选择菜单:");
            string str_menu_num = Console.ReadLine();
            switch (str_menu_num)
            {
                case "1":
                    Console.WriteLine("魔法师幸运抽奖系统 > 注册");
                    string [] result = Reg();
                    if (string.IsNullOrEmpty(result[0]))
                    {
                        isReg = false;
                       
                    }
                    else
                    {
                        userName = result[0];
                        password = result[1];
                        cardNum = result[2];
                        isReg = true;
                    }

                    break;
                case "2":
                    if (isReg)
                    {
                        Console.WriteLine("魔法师幸运抽奖系统 > 登录");
                        for (int i = 1; i <= 3; i++)
                        {
                            Console.Write("第{0}/3次,请输入用户名：",i);
                            string un = Console.ReadLine();
                            Console.Write("第{0}/3次，请输入密码:",i);
                            string pw = Console.ReadLine();
                            if (userName == un && password == pw)
                            {
                                Console.WriteLine("欢迎您:{0}", userName);
                                isLogin = true;
                                break;
                            }
                            else
                            {
                                isLogin = false;
                                continue;
                            }
                        }
                        
                    }
                    else
                    {
                        Console.WriteLine("您没有注册，请先注册后再登录");
                    }

                    
                    break;
                case "3":
                   
                    if (isLogin)
                    {
                        Console.WriteLine("魔法师幸运抽奖系统 > 抽奖");
                        Console.Write("请输入会员卡号:");
                        string str_card_num = Console.ReadLine();
                        string[] lucknums = new string[5];
                        Console.Write("本日的幸运数字为:");
                        for (int i = 0; i < lucknums.Length; i++)
                        {
                            lucknums[i] = rd.Next(min, max).ToString();
                            Console.Write(lucknums[i] + "\t");
                        }
                        int index = Array.IndexOf(lucknums, str_card_num);
                        if (index == -1)
                        {
                            Console.WriteLine("抱歉，您不是本日的幸运会员");
                        }
                        else
                        {
                            Console.WriteLine("恭喜您，您中奖了了~~~");
                        }
                    }
                    else
                    {
                        Console.WriteLine("您没有登录，请先登录后再抽奖");
                    }


                    break;
                default:
                    Console.WriteLine("您的输入有误~");
                    break;
            }

            Console.Write("继续吗？(y/n)");
            flag = Console.ReadLine();
        }while(flag == "y"||flag == "Y");

        Console.WriteLine("系统退出，谢谢使用");


        Console.ReadKey();
    }

    /**
     * 注册
     * */
    static string[] Reg()
    {
        string[] ret = new string[3];

        Random rd = new Random();
        int max = 9999;
        int min = 1000;

        Console.WriteLine("请填写个人注册信息");
        Console.Write("用户名:");
        string userName = Console.ReadLine();//获得用户输入的用户名
        
        if (userName == "admin")
        {
            Console.WriteLine("admin帐户已被占用");
            return ret;
        }
        
        //Console.WriteLine();
        Console.Write("密码:");
       string password = Console.ReadLine();  //获得用户输入的密码
        //用随机的数作为卡号
       string cardNum = rd.Next(min, max).ToString();
        Console.WriteLine("注册成功，请记好您的会员卡号");
        Console.WriteLine("用户名\t密码\t会员卡号");
        Console.WriteLine("{0}\t{1}\t{2}", userName, password, cardNum);

        ret[0] = userName;
        ret[1] = password;
        ret[2] = cardNum;

        return ret;

    }
}

}