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 startspublic int RacetrackLength = 525;       //How long the racetrack ispublic PictureBox MyPictureBox = null;      //My PictureBox objectpublic int Location = 0;        //My Location on the racetrackpublic Random Randomizer;       //An instance fo Randompublic 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 linePoint 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 namepublic Bet MyBet;       //An instance of Bet() that has his betpublic int Cash;        //How much cash he has//The last two fields are the guy's GUI controls on the formpublic RadioButton MyRadioButton;   //My RadioButtonpublic Label MyLabel;   //My Labelpublic 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 zeropublic 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 betif (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 outCash += MyBet.PayOut(Winner);}}
}

Bet类的代码：

namespace DogRace
{class Bet{public int Amount;      //The amount of cash that was betpublic int Dog;         //The number of the dog the bet is onpublic Guy Bettor;      //The guy who placed the betpublic 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