C# 如何从按钮单击事件中获取返回值？

我刚开始学C。我看到一个老问题，有人试图制造一台可口可乐机，这似乎是一个很好的练习

但我被钱扣卡住了。我不知道如何将一个按钮代表的金额存储在一个变量中，该变量可以通过ColaMachine方法访问

我有以下代码：

using System;
using System.Windows.Forms;
using System.Drawing;

namespace QuickSharp
{
    public class ColaMachine : Form
    {
        public ColaMachine()
        {
            this.Text = "Cola Machine";
            this.Size = new Size(450 , 500);

            //Money & Money Buttons   

            Label Money;
            Money = new Label();
            Money.Text = "Insert Coins Here:";
            Money.Location = new Point(20, 100);
            this.Controls.Add(Money);

            Button MoneyButton1;
            MoneyButton1 = new Button();
            MoneyButton1.Text = "€0,05";
            MoneyButton1.Location = new Point(28,125);
            MoneyButton1.Click += new System.EventHandler(this.MoneyButton1_Click);
            this.Controls.Add(MoneyButton1);

            Button MoneyButton2;
            MoneyButton2 = new Button();
            MoneyButton2.Text = "€0,10";
            MoneyButton2.Location = new Point(28,165);
            MoneyButton2.Click += new System.EventHandler(this.MoneyButton2_Click);
            this.Controls.Add(MoneyButton2);

            Button MoneyButton3;
            MoneyButton3 = new Button();
            MoneyButton3.Text = "€0,20";
            MoneyButton3.Location = new Point(28,205);
            MoneyButton3.Click += new System.EventHandler(this.MoneyButton3_Click);
            this.Controls.Add(MoneyButton3);

            Button MoneyButton4;
            MoneyButton4 = new Button();
            MoneyButton4.Text = "€0,50";
            MoneyButton4.Location = new Point(28,245);
            MoneyButton4.Click += new System.EventHandler(this.MoneyButton4_Click);
            this.Controls.Add(MoneyButton4);

            Button MoneyButton5;
            MoneyButton5 = new Button();
            MoneyButton5.Text = "€1,00";
            MoneyButton5.Location = new Point(28,285);
            MoneyButton5.Click += new System.EventHandler(this.MoneyButton5_Click);
            this.Controls.Add(MoneyButton5);

            Button MoneyButton6;
            MoneyButton6 = new Button();
            MoneyButton6.Text = "€2,00";
            MoneyButton6.Location = new Point(28,325);
            MoneyButton6.Click += new System.EventHandler(this.MoneyButton6_Click);
            this.Controls.Add(MoneyButton6);

            // Drinks & Drink Buttons

            Label Drinks;
            Drinks = new Label();
            Drinks.Text = "Choose Your Drink:";
            Drinks.Location = new Point(315 , 100);
            Drinks.AutoSize = true;
            this.Controls.Add(Drinks);

            Button DrinkButton1;
            DrinkButton1 = new Button();
            DrinkButton1.Text = "Coca-Cola";
            DrinkButton1.Location = new Point(328,125);
            this.Controls.Add(DrinkButton1);

                        Button DrinkButton2;
            DrinkButton2 = new Button();
            DrinkButton2.Text = "Coca-Cola Light";
            DrinkButton2.Location = new Point(328,165);
            this.Controls.Add(DrinkButton2);

                        Button DrinkButton3;
            DrinkButton3 = new Button();
            DrinkButton3.Text = "Fanta";
            DrinkButton3.Location = new Point(328,205);
            this.Controls.Add(DrinkButton3);

                        Button DrinkButton4;
            DrinkButton4 = new Button();
            DrinkButton4.Text = "Sprite";
            DrinkButton4.Location = new Point(328,245);
            this.Controls.Add(DrinkButton4);

                        Button DrinkButton5;
            DrinkButton5 = new Button();
            DrinkButton5.Text = "Spa Blauw";
            DrinkButton5.Location = new Point(328,285);
            this.Controls.Add(DrinkButton5);

                        Button DrinkButton6;
            DrinkButton6 = new Button();
            DrinkButton6.Text = "Red Bull";
            DrinkButton6.Location = new Point(328,325);
            this.Controls.Add(DrinkButton6);

            //Header & Machine Display

            Label Header;
            Header = new Label();
            Header.Text = "Coca-Cola Machine";
            Header.Font = new Font("Arial" , Header.Font.Size +5);
            Header.ForeColor = Color.DarkRed;
            Header.Location = new Point(132, 20);
            Header.AutoSize = true;
            this.Controls.Add(Header);



            TextBox TextBox1 ;
            TextBox1 = new TextBox();

            if(InsertedCoins == 0.00)
                TextBox1.Text = "Buy Your Ice Cold Drinks Here!";
            else
                TextBox1.Text = "Inserted Coins: €" + InsertedCoins;

            TextBox1.BackColor = Color.Black;
            TextBox1.ForeColor = Color.Red;
            TextBox1.Font = new Font("Arial" , TextBox1.Font.Size +3);
            TextBox1.ReadOnly = true;
            TextBox1.Size = new Size(210,300);
            TextBox1.Location = new Point(112,50);

            // I tried to get the text scrolling here... :)
            TextBox1.SelectionStart = TextBox1.Text.Length;
            TextBox1.ScrollToCaret();
            TextBox1.Refresh();

            this.Controls.Add(TextBox1);
        }


        public double InsertedCoins;

        // Money Button Click Events

        private void MoneyButton1_Click(object sender, EventArgs e)
        {
            InsertedCoins = InsertedCoins + 0.05;
        }

        private void MoneyButton2_Click(object sender, EventArgs e)
        {
            InsertedCoins = InsertedCoins + 0.10;
        }

        private void MoneyButton3_Click(object sender, EventArgs e)
        {
            InsertedCoins = InsertedCoins + 0.20;
        }

        private void MoneyButton4_Click(object sender, EventArgs e)
        {
            InsertedCoins = InsertedCoins + 0.50;
        }

        private void MoneyButton5_Click(object sender, EventArgs e)
        {
            InsertedCoins = InsertedCoins + 1.00;
        }

        private void MoneyButton6_Click(object sender, EventArgs e)
        {
            InsertedCoins = InsertedCoins + 2.00;
        }

        private static void Main()
        {

            ColaMachine Scherm;
            Scherm = new ColaMachine();
            Application.Run(Scherm);
        }
    }
}

---

此外，如果您对我的常规编程有任何建议（例如，让其他试图阅读我的代码的人更容易理解），请告诉我

您可以存储每个按钮i按钮标记属性的金额，并在eventhandler中使用以下代码读取金额：

void ValueButton_Click(object sender, EventArgs e)
{
  Button button = sender as Button;
  if (button == null) return;
  if (button.Tag == null) return;
  double amount = (double)button.Tag;

  // Process the amount here....
  InsertedCoins += amount; 
}

---

先想想： 你应该把问题分为两类（类测试和类ColaMachine）

看起来像是：

public class ColaMachine : Form
{
  public ColaMachine()
  {  
     ...
  }
}

public class Test 
{
   private static void Main()
   {
      ColaMachine Scherm;
      Scherm = new ColaMachine();
      Application.Run(Scherm);
   }
}

下一个：如果要返回私有的变量，请使用属性。IC将是一个公共方法（属性）。InsertedCoins将是一个私有变量

public double IC
{
   get
   {
      return InsertedCoins;
    }
   set
   {
      InsertedCoins = value;
   }
}

---

别忘了，机器有很多状态。你应该使用设计模式，确切地说是状态模式。当我想到一台可乐机时，我看到机器中每种饮料都有一个按钮，但不同金额的饮料没有按钮。也许你的意思是一瓶可乐要50美分，所以按可乐按钮我要收50美分

按钮和事件处理程序

当您按下屏幕上的按钮时，会生成一个单击事件。您需要编写一个方法来响应该单击。我们用来响应事件的任何方法（一般来说）都称为事件处理程序。您必须告诉您的程序哪些按钮与哪些事件处理程序一起使用。我们称之为注册事件处理程序

按照惯例，如果您的按钮名为“CokeButton”，那么与该特定按钮关联的事件处理程序将命名为“CokeButton\u ClickHandler”。或者类似的

一般建议

思考您正在建模的东西，并在代码中定义东西以反映真实世界。模型中的内容通常以类、类属性和类字段结束。这些事情通常会在适当的类中作为方法结束。然后想想这些东西是如何相互作用的

在开始编写代码之前，您不需要了解可乐机的所有信息。你应该一次写一点点，测试它们，然后在你测试过的基础上构建。不要编写大量复杂的代码，然后进行测试。你会在追逐你的尾巴时绕圈子。写一点，测试一点，重复一遍<现在听我说，以后相信我；写一点，测试一点，然后重复。现在和永远都要听从这个建议

下面是我对可乐机的看法。首先是可乐机本身

public class CokeMachine {}

可乐机有一个钱槽、一个回程槽和饮料按钮。我真的不能把钱放进投币口，所以我会说我会在文本框中输入。然后我点击一个按钮，可乐就会自动分配。我觉得我已经定义了足够多的模型，可以开始了。关于可乐机还有很多其他的事情，但我现在不想担心它们

但我需要知道每种饮料的价格。

嗯，好的。然后必须有“CokeCost”、“7UpCost”等字段。所以定义它们吧！我们将在前进的过程中找出如何以及在何处使用它们

   public class CokeMachine {
     Button Coke;
     Button 7Up;
     Button RootBeer;
     TextBox MoneySlot;

     double CokeCost = .75;
     double 7UpCost = .65;
}

我说过按钮需要处理程序，所以我们至少可以编写一些代码外壳。我希望他们都会以同样的方式工作，所以我现在将重点放在一个方面。请注意，在编写代码时，我意识到必须处理的其他事情。我会添加注释，调用还不存在的方法，等等

   public class CokeMachine {
     Button Coke;
     Button 7Up;
     Button RootBeer;
     TextBox MoneySlot;

     double CokeCost = .75;
     double 7UpCost = .65;

     // "wiring up" the coke button click event to it's handler.
     // We do this in C# by declaring an new EventHandler object (a .NET framework supplied class)
     // and we pass in the name of our method as a parameter.
     // This new EventHandler is *added* to the button's click event.
     // An event can have multiple handlers, that's why we do "+="
     // instead of just "=". Otherwise we would have accidentally "unhooked" any
     // previously registered handlers.
     Coke.Click += new EventHandler(Coke_ClickHandler);

     // this is the .NET event handler method signature.
     Public void Coke_ClickHandler (object sender, EventArgs args){
          if (MoneySlot.Value >= CokeCost) {
             DispenseDrink();
             // How do I handle returning change? Maybe DispenseDrink() can do that.
          }else {
             // tell customer to put in more money
          }
     }

     private void DispenseDrink() {
       // An empty method is enough to get it to compile so for now that's fine.
       // I need to test the Coke_EventHandler logic that I've written so far.
     }

  }

现在我需要测试到目前为止我写的东西。之后，我需要决定下一步的重点。但是要意识到，当您在编写依赖于已经编写的代码的新代码时，如果现有代码还没有经过测试——而现在您看到了错误，那么您只会让自己更加困难。您可以在代码更简单的时候进行测试。现在有更多，更复杂，更难调试和修复

建议，第二部分

冒着把事情搞砸的风险，我给出以下我最初的答案：

您可以看到每个饮料按钮都做相同的事情，根据上面的代码，我们将为每个按钮反复编写相同的逻辑。如果有什么需要改变，我们必须在任何地方都改变它

更一般的建议

一种面向对象的编程启发式方法是封装保持不变的程序。您应该始终注意一些地方，这些地方可能是通用代码的候选者

我想强调的是，这种常见的按钮行为对我来说并不是很明显。只有在我写了上面的代码之后，我才开始认为我所有的饮料按钮处理程序看起来都是一样的，我意识到在一台真正的饮料机上，它们的行为确实是一样的。我的编码蜘蛛侠意识告诉我，当代码反映真实事物的可识别行为时，这绝对是一件好事（双关语！）

重构

实际上，这是一个技术术语，意思是对现有代码进行修改，使其更灵活、可重用、可读性更强，总之是可维护的

重构应该一直在你的思维过程中。但要确保你有做出任何改变的正当理由。重塑代码是软件开发中一个正常的、不可分割的部分

让我们通过提取方法进行重构

枚举数

我讨厌像上面用“可乐”那样用字符串。打字错误和大小写（即上/下）可能会导致Visual Studio无法捕捉到的问题。当我有一个有限的物品清单-各种饮料-我真的喜欢使用enumerati

     Public void Coke_ClickHandler (object sender, EventArgs args){
          PurchaseDrink("Coke", CokeCost);
     }

     // now we have a method that stands out and says THIS is how it works
     // and a single point of change, rather than ump-teen button handlers.
      private PurchaseDrink (string whatKind, double cost) {

         // all I did so far is move the code and change "Cokecost" to "cost"
         // Now I'm beginning to think I may need to pass "whatKind" to
         // DispenseDrink() - but first I need to test the changes I've
         // made at this level.
         // ***** and since I already tested the code when I 1st wrote it,
         // this refactoring will be easier & quicker to test.. GET IT??!! ******

         if (MoneySlot.Value >= cost) {
             DispenseDrink();
             // How do I handle returning change? Maybe DispenseDrink() can do that.
          }else {
             // tell customer to put in more money
          }
     }

     private void DispenseDrink() {
       // An empty method is enough to get it to compile so for now that's fine.
       // I need to test the Coke_EventHandler logic that I've written so far.
     }