帮我读解一下这个自定义控件.

Question

// Composite.cs.
using System;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;namespace CustomControls 
{
      
      public class Composite : Control, INamingContainer 
      {
            private int number = 100;
            private Label label;
            
            public int Number //PPP1
            {
                  get
                  {
                        return number;
                  }
                  set
                  {
                        number = value;
                  }
            }
            
            private int Sum 
            {
                  get 
                  {
                        EnsureChildControls();
                        return Int32.Parse(((TextBox)Controls[1]).Text) + 
                              Int32.Parse(((TextBox)Controls[4]).Text);
                  }
                  
            }            public string Text //PPP2
            {
                  get
                  {
                    EnsureChildControls();
                        return label.Text;
                  }
                  set
                  {
                    EnsureChildControls();
                        label.Text = value;
                  }
            }
            
            
            public event CheckEventHandler2 Check;  //PPP3 这一行可理解为定义一个事件类CheckEventHandler2的实例Check吗?
            
            protected virtual void OnCheck(CheckEventArgs2 ce)
            {
                  if (Check != null) //这句是不是查看有无创建Check实例?
                  {
                        Check(this,ce); // 这个调用了实例那个方法? 
                 }
            }
            
            protected override void CreateChildControls() 
            {
                  
                  Controls.Add(new LiteralControl("<h3>第一个数 : "));
                  
                  TextBox box1 = new TextBox();
                  box1.Text = "0";
                  Controls.Add(box1);
                  
                  Controls.Add(new LiteralControl("</h3>"));
                  
                  Controls.Add(new LiteralControl("<h3>第二个数 : "));
                  
                  TextBox box2 = new TextBox();
                  box2.Text = "0";
                  Controls.Add(box2);
                  
                  Controls.Add(new LiteralControl("</h3>"));
                  
                  Button button1 = new Button();
                  button1.Text = "提交";
                  Controls.Add(new LiteralControl("<br>"));
                  Controls.Add(button1);
                  button1.Click += new EventHandler(this.ButtonClicked);
                  
                  Controls.Add(new LiteralControl("<br><br>"));
                  label = new Label();
                  label.Height = 50;
                  label.Width = 500;
                  label.Text = "输入数后占击按钮提交.";
                  Controls.Add(label);
                  
            }
            
            protected override void OnPreRender(EventArgs e)
            {
                  ((TextBox)Controls[1]).Text = "0";
                  ((TextBox)Controls[4]).Text = "0";
            }
            
            private void ButtonClicked(Object sender, EventArgs e)
            {
                  OnCheck(new CheckEventArgs2(Sum - Number));
            }
      }
}// CheckEvent.cs.
// Contains the code for the custom event data class CheckEventArgs.
// Also defines the event handler for the Check event.
using System;namespace CustomControls
{
      public class CheckEventArgs2 : EventArgs
      {
            private bool match = false;
            
            public CheckEventArgs2 (int difference)
            {
                  if (difference == 0)
                  {
                        match = true;
                  }
            }
            public bool Match
            {
                  get
                  {
                        return match;
                  }
            }
      }
      
      public delegate void CheckEventHandler2(object sender, CheckEventArgs2 ce);//这一句有什么用,ce是什么?
}还有就是为什么要把判断Sum - Number是否等于零这个简单操作要写成一个类呢?作用是什么?
应用层页:
<%@ Register TagPrefix="Custom" Namespace="CustomControls" Assembly = "CustomControls" %>
<html>
<script language="C#" runat=server>      private void Sum_Checked2 (Object sender,CheckEventArgs2 e) //这里为什么要有:Object sender,CheckEventArgs2 e
        {
          if (e.Match == true)
           Composite3.Text = "<h2>通过啦!!! </h2>";
          else 
           Composite3.Text = "对不起,你输入的两个数加起来不等于" +
            "那隐藏数.";      }           
      
</script>
            
<body><h1> The Mystery Sum Game </h1><br>
                  
<form runat=server>                             
<Custom:Composite id = "Composite3" OnCheck = "Sum_Checked2"  runat = server/>                                                                          
</form>                                               
</body>                                         
</html>

Answer 1

public delegate void CheckEventHandler2(object sender, CheckEventArgs2 ce);//这一句有什么用,ce是什么?
---------------------------------------
声名一委托，ce是 CheckEventArgs的实例，从EventArgs派生---------------------------------------------------
            public event CheckEventHandler2 Check;  //PPP3 这一行可理解为定义一个事件类CheckEventHandler2的实例Check吗?
----------------------------------
声明一CheckEventHandler2委托类的事件还有就是为什么要把判断Sum - Number是否等于零这个简单操作要写成一个类呢?作用是什么?
-------------------------------------------是手段而不是目的  
Y就是一的关于委托，事件小例子