一个小游戏

    小弟初学C#和面向对象的思想，闲来无事就写个小程序练手，写完后感觉还是没有领悟面向对象的精髓，设计上还有很多毛病，还请各位达人不吝赐教。
    这个游戏是仿造文曲星上的猜数字游戏，程序先生成一个4位无重复的随机数，再要求玩家输入4位数字并将输入的数字入随机数进行比较。若是输入的数字中有随机数中的数字，但是位置与随机数不同则可得到指示B；若是输入的数字中有随机数中的数字，且位置与随机数相同则可得到指示（如随机数为1234，输入的数为7891 则结果是0A1B；输入为1243，则结果为2A2B），玩家在指定的次数内猜中随机数就算获胜。这是个逻辑性比较强的游戏，希望大家喜欢。

using System;

namespace GuessNumeral
{
    /// <summary>
    /// GuessNumeral 的摘要说明。
    /// </summary>
    public class GuessNumeral
    {
        private string _first;//随机数的第一位
        private string _second;//随机数的第二位
        private string _third;//随机数的第三位
        private string _fouth;//随机数的第四位
        private string _numstr;//随机数字符串
        private int[] array_a;//结果标识
        private int[] array_b;//结果标识
        private int ramnum;//随机数
        private int level;//游戏难度
        protected int count;//执行次数
        private string input;//玩家输入的字符
        public void Initialize()//游戏初始化
        {
            array_a=new int[]{1,1,1,1,1,1,1,1,1,1};
        }
        public int CreatRandom()//生成随机数
        {
            Random ram=new Random();
            ramnum=ram.Next(0,10);
            if(array_a[ramnum]==0)
            {this.CreatRandom();}
            return ramnum;
        }
        public void CreatRamstr()//组成字符串
        {
            string numstr;
            numstr="";
            for(int i=0;i<4;i++)
            {
                int num;
                num=this.CreatRandom();
                array_a[num]=0;
                numstr=numstr+num.ToString();
            }
            this.Numstr=numstr;
        }
        public void SetNumber()//分别给每位属性赋值
        {
            _first=this.Numstr.ToString().Substring(0,1);
            _second=this.Numstr.ToString().Substring(1,1);
            _third=this.Numstr.ToString().Substring(2,1);
            _fouth=this.Numstr.ToString().Substring(3,1);
        }
        public void GetInput()//获取玩家输入的字符并判断是否合适
        {  
            bool upshot;
            upshot=true;
            array_b=new int[]{1,1,1,1,1,1,1,1,1,1};
            input="";
            Console.WriteLine("请输入四位无重复的数字：");
            input=Console.ReadLine();
            if (input.Length!=4)
            {
                this.GetInput();
            }
            else
            {
                for (int i=0;i<4;i++)
                {
                    try
                    {
                    if    (array_b[Convert.ToInt32(input.ToString().Substring(i,1))]==0)
                        {    
                            upshot=false;
                        }
                        else
                        {
                            array_b[Convert.ToInt32(input.ToString().Substring(i,1))]=0;
                        }
                    }
                    catch
                    {
                        upshot=false;
                    }
                }
            }
             if (upshot==false)
            {    
                this.GetInput();
            }
        }
        public int Execute()//对输入的字符进行一次判断并给出结果
        {
            int result_a=0;
            int result_b=0;
            int end_sign=0;
            if (count!=0)
            {
                for(int i=0;i<4;i++)
                {
                    if (input.ToString().Substring(i,1)==this.First)
                        result_b=result_b+1;
                    if (input.ToString().Substring(i,1)==this.Second)
                        result_b=result_b+1;
                    if (input.ToString().Substring(i,1)==this.Third)
                        result_b=result_b+1;
                    if (input.ToString().Substring(i,1)==this.Fouth)
                        result_b=result_b+1;
                }
                if (input.ToString().Substring(0,1)==this.First)
                {    
                    result_a=result_a+1;
                    result_b=result_b-1;
                }
                if (input.ToString().Substring(1,1)==this.Second)
                {    
                    result_a=result_a+1;
                    result_b=result_b-1;
                }
                if (input.ToString().Substring(2,1)==this.Third)
                {    
                    result_a=result_a+1;
                    result_b=result_b-1;
                }
                if (input.ToString().Substring(3,1)==this.Fouth)
                {    
                    result_a=result_a+1;
                    result_b=result_b-1;
                }
                if (result_a==4)
                {
                    Console.WriteLine("正确,人才阿!~~~");
                    end_sign=1;
                    return end_sign;
                }
                Console.WriteLine(result_a.ToString()+"A"+result_b.ToString()+"B");
                count--;
                Console.WriteLine("你还有"+(count+1).ToString()+"次机会!");
                end_sign=0;
                return end_sign;
            }
            else    
                Console.WriteLine("Sorry,you lose!");
                Console.WriteLine("正确结果是: "+this.Numstr.ToString());
            end_sign=2;
            return end_sign;
            
        }
        public void SetLevel()//设定游戏难度
        {
            string level_str;
            Console.WriteLine("请选择游戏难度：!(1-简单;2-普通;3-困难)");
            level_str=Console.ReadLine();
            try
            {
                level=Convert.ToInt32(level_str);
            }
            catch
            {
                Console.WriteLine("请输入你想选择的难度的标号");
                this.SetLevel();
            }
            if (level!=1&level!=2&level!=3)
            {
                this.SetLevel();
            }
            if (level==1)
            {
                count=9;
            }    
            if (level==2)
            {
                count=7;
            }
            if (level==3)
            {
                count=5;
            }
        }
        public void ReStart()//重新运行游戏
        {
            Console.WriteLine("Do you want try again?(Y/N)");
            string mark=Console.ReadLine();
            if(mark=="y"||mark=="Y")
                this.GameExecute();
            else if (mark=="n"||mark=="N")
            {
                Console.WriteLine("Are you sure exit this game?(Y/N) ");
                string remark=Console.ReadLine();
                if (remark=="y"||remark=="Y")
                    Console.WriteLine("886!");
                else if (remark=="n"||remark=="N")
                    this.GameExecute();
                else
                    this.ReStart();
            }
            else if(mark!="y"||mark!="Y"||mark!="n"||mark!="N")
                this.ReStart();
        }
        public void GameExecute()//游戏执行主程序
        {
            this.Initialize();
            this.SetLevel();
            this.CreatRamstr();
            Console.WriteLine(this.Numstr.ToString());
            this.SetNumber();
            int end=0;
            while (end!=1&end!=2)
            {
                this.GetInput();
                end=this.Execute();
            }
        }
        public string First
        {
            get{return _first;}
            set{_first=value;}
        }
        public string Second
        {
            get{return _second;}
            set{_second=value;}
        }
        public string Third
        {
            get{return _third;}
            set{_third=value;}
        }
        public string Fouth
        {
            get{return _fouth;}
            set{_fouth=value;}
        }
        public string Numstr
        {
            get{return _numstr;}
            set{_numstr=value;}
        }
    }
    public class GameStart
    {
        [STAThread]
        static void Main(string[] args)
        {
            GuessNumeral gn=new GuessNumeral();
            gn.GameExecute();
            gn.ReStart();
        }
    }
}