Head First C# 实验室 赛狗日

话说这是第一次用Markdown编辑器，代码的高亮方式好奇怪，谁来帮帮我？

本人正在新学C#，这是Head First C# （第二版）的第一个实验，要求写一个模拟赛狗的程序（为什么是赛狗而不是赛马 =_=）。题目我就不多介绍了，因为我假定你已经知道题目了，要不然你也不会来看这篇博客。

首先来一张程序的界面

这个程序需要自己创建三个类，Greyhound，Guy，和Bet，要搞清楚这三个类分别是干什么的。

Greyhound就是狗啦，它主要用来控制四条狗的位置。其中TakeStartingPosition()是将狗放回起点位置；而Run()则是让狗移动，类型为bool，如果这条狗到达了终点，就返回true。在后面的使用中，要用一个数组来放四条狗。狗每跑一步，都要检测Run()的返回值，一旦为true了，就结束比赛，同时把当前这条狗记为冠军。

Guy类是人，下注的人。而Bet类则表示一个下注。这两个类有些麻烦，因为Guy类中包含一个Bet类字段MyBet，而Bet类中也包含一个Guy类字段Bettor，真是晕。让我来慢慢解释。

首先Guy类，它包含字段Name，Cash，分别指人的名字以及他所拥有 的现金，而MyBet则表示一次下注。如果他还没有下注，则MyBet=null；如果他下了注，MyBet类就会引用一个Bet类实例。另外MyRadioButton和MyLabel分别为了引用界面上的RadioButton和Label标签。Guy类的几个方法，UpdateLabels()就是更新界面上显示的信息的；PlaceBet()就是让MyBet新建一个实例，表示这个下注了；相反，ClearBet()则是把MyBet引用的内容释放掉，在C#中只要让MyBet=null就可以了，终于不需要C++里的delete了；最后的Collect()方法，就是根据这个人是赢了还是输了来改变他的现金Cash。

至于Bet类，它并不是指某一样东西，而是指一件事情，即下注。所以它有字段Amount和Dog，分别下注的金额以及押的狗的编号。而它包含一个Guy类Bettor，这是指这个注是谁下的。例如，假设已经有了一个实例化的Guy类叫Joe，然后Joe下了一个注，为了方便，给这个“注”取个名字叫Bet1（我随便取的名字），那么就有这样一种关系

Joe.MyBet = Bet1;Bet1.Bettor = Joe;

上面的只是关系示例，只是为了搞明白关系，具体代码中是没Bet1这种名字的。Joe下注这个操作写成代码是 Joe.PlaceBet()，这里面的实现代码是Joe.MyBet = new Bet(); 当然，要加上参数Amount和Dog，我这里省略了。然后再让MyBet.Bettor = this。其中的this在这里就是指Joe。在C#里可以用列表初始化类，所以在这个PlaceBet()方法里可以直接写成

MyBet = new Bet { Amount = Amount, Dog = Dog, Bettor = this };

Bet里的GetDescription()方法，是返回一个字符串描述，指出是谁在下注，他押的是哪条狗。而PayOut(int Winner)方法，如果Winner等于当前Bet实例里的Dog，表示押中了，就返回Amount，否则返回-Amount，这是为了给Guy类的Collect()方法调用的。

下面是Greyhound类的代码：

using System;using System.Windows.Forms;using System.Drawing;namespace DogRace{    class Greyhound    {        public int StartingPosition = 12;       //Where my PictureBox starts        public int RacetrackLength = 525;       //How long the racetrack is        public PictureBox MyPictureBox = null;      //My PictureBox object        public int Location = 0;        //My Location on the racetrack        public Random Randomizer;       //An instance fo Random        public bool Run()        {            /* Move forward either 1, 2, 3 or 4 spaces at random             * Update the position of my PictureBox on the form             * Return true if I won the race             */            Point p = MyPictureBox.Location;            p.X += Randomizer.Next(20);            MyPictureBox.Location = p;            Location = p.X - StartingPosition;            if (Location >= RacetrackLength)            {                return true;            }            else            {                return false;            }        }        public void TakeStartingPosition()        {            //Reset my location to the start line            Point p = MyPictureBox.Location;            p.X = StartingPosition;            MyPictureBox.Location = p;        }    }}

Guy类的代码：

using System.Windows.Forms;namespace DogRace{    class Guy    {        public string Name;     //The guy's name        public Bet MyBet;       //An instance of Bet() that has his bet        public int Cash;        //How much cash he has        //The last two fields are the guy's GUI controls on the form        public RadioButton MyRadioButton;   //My RadioButton        public Label MyLabel;   //My Label        public void UpdateLabels()        {            //Set my label to my bet's description, and the label on my radio button to show my cash ("Joe has 43 bucks")            if (MyBet != null)            {                MyLabel.Text = MyBet.GetDescription();            }            else            {                MyLabel.Text = Name + " hasn't placed a bet";            }            MyRadioButton.Text = Name + " has " + Cash + " bucks";        }        //Reset my bet so it's zero        public void ClearBet()        {            MyBet = null;            UpdateLabels();        }        public bool PlaceBet(int Amount, int Dog)        {            //Place a new bet and store it in my bet field            //Return true if the guy had enough money to bet            if (Amount <= Cash && Amount > 0)            {                MyBet = new Bet { Amount = Amount, Dog = Dog, Bettor = this };                return true;            }            else            {                return false;            }        }        public void Collect(int Winner)        {            //Ask my bet to pay out            Cash += MyBet.PayOut(Winner);        }    }}

Bet类的代码：

namespace DogRace{    class Bet    {        public int Amount;      //The amount of cash that was bet        public int Dog;         //The number of the dog the bet is on        public Guy Bettor;      //The guy who placed the bet        public string GetDescription()        {            //Return a string that says who placed the bet, how much cash was bet, and which dog he bet on ("Joe bets 8 on dog #4"). If the amount is zero, no bet was placed ("Joe hasn't placed a bet").            if (Amount > 0)            {                return Bettor.Name + " bets " + Amount + " on dog #" + Dog;            }            else            {                return Bettor.Name + " hasn't placed a bet";            }        }        public int PayOut(int Winner)        {            //The parameter is the winner of the race. If the dog won, return the amount bet. Otherwise, return the negative of the amount bet.            if (Winner == Dog)            {                return Amount;            }            else            {                return -Amount;            }        }    }}

然后是界面的代码，我用的名字还是Form1.....

using System;using System.Windows.Forms;namespace DogRace{    public partial class Form1 : Form    {        Greyhound[] dogs;        Guy[] bettors;        public Form1()        {            InitializeComponent();            Random random = new Random();            dogs = new Greyhound[4]            {                new Greyhound() {MyPictureBox=pictureBox0, Randomizer=random },                new Greyhound() {MyPictureBox=pictureBox1, Randomizer=random },                new Greyhound() {MyPictureBox=pictureBox2, Randomizer=random },                new Greyhound() {MyPictureBox=pictureBox3, Randomizer=random }            };            bettors = new Guy[3]            {                new Guy() {Name="Joe", Cash=50, MyLabel=lblJoeBet, MyRadioButton=radioJoe },                new Guy() {Name="Bob", Cash=75, MyLabel=lblBobBet, MyRadioButton=radioBob },                new Guy() {Name="Al",  Cash=45, MyLabel=lblAlBet,  MyRadioButton=radioAl }            };            foreach (var guy in bettors)            {                guy.UpdateLabels();            }        }        private void radioJoe_CheckedChanged(object sender, EventArgs e)        {            labName.Text = "Joe";            numericUpDown1.Maximum = bettors[0].Cash;        }        private void radioBob_CheckedChanged(object sender, EventArgs e)        {            labName.Text = "Bob";            numericUpDown1.Maximum = bettors[1].Cash;        }        private void radioAl_CheckedChanged(object sender, EventArgs e)        {            labName.Text = "Al";            numericUpDown1.Maximum = bettors[2].Cash;        }        private void btnBets_Click(object sender, EventArgs e)        {            foreach (var bettor in bettors)            {                if (bettor.MyRadioButton.Checked)                {                    bettor.PlaceBet((int)numericUpDown1.Value, (int)numericUpDown2.Value);                    bettor.UpdateLabels();                }            }        }        private void btnRace_Click(object sender, EventArgs e)        {            //先检查是否所有人都下注            bool allGuysBet = true;            foreach (var bettor in bettors)            {                if (bettor.MyBet == null)                {                    allGuysBet = false;                }            }            if (!allGuysBet)            {                MessageBox.Show("Someone hasn't bet");                return;            }            //如果都下注，就开始比赛            this.btnRace.Enabled = false;            this.btnBets.Enabled = false;            bool hasAWinner = false;            int winner = -1;            while (!hasAWinner)            {                for (int i = 0; i < 4; i++)                {                    hasAWinner = dogs[i].Run();                    if (hasAWinner)                    {                        winner = i + 1;                        MessageBox.Show("dog #" + winner + " win!");                        break;                    }                    System.Threading.Thread.Sleep(20);                    Application.DoEvents();                }            }            //比赛结束，统计结果并将狗复位            foreach (var bettor in bettors)            {                bettor.Collect(winner);                bettor.ClearBet();                bettor.UpdateLabels();            }            foreach (var dog in dogs)            {                dog.TakeStartingPosition();            }            this.btnRace.Enabled = true;            this.btnBets.Enabled = true;        }    }}

至于界面设计部分的代码，我就不放了，太长了，并不是重点。

更新：我把完整的代码放在了我的Github上，欢迎访问 DogRace