如何订阅Form的自定义事件

 　　Window Form类有很多的属性/方法和事件,其中事件属于一种发布订阅模式 。订阅发布模式定义了一种一对多的依赖关系，让多个订阅者对象同时监听某一个主体对象。这个主体对象在自身状态变化时，会通知所有订阅者对象，使它们能够自动更新自己的状态。 当一个对象的改变需要同时改变其他对象，而且无需关心具体有多少对象需要改变时，就特别适合用此种模式。本文将演示如何在窗体上自定义一个事件(custom event) : 

1 自定义一个CustomEventArgs类

　　一般自定义的事件都有一个参数,继承自EventArgs.此处我们自定一个CustomEventArgs,类中通过自定义字段来存储参数的值:

 1 using System;  2 using System.Collections.Generic;  3 using System.Linq;  4 using System.Text;  5 
 6 namespace CustomEventsDemo  7 {  8     public class CustomEventArgs:EventArgs  9  { 10         //自定义字段用于存储值
11         public object Tag; 12         public string Message; 13         public CustomEventArgs() 14  { 15             
16  } 17         public CustomEventArgs(string message, object tag) 18  { 19             Message = message; 20             Tag = tag; 21  } 22  } 23 }

 2 自定义一个事件

 　　接下来我们创建一个FormPublisher窗体,然后用 event EventHandler<CustomEventArgs> customEvent;event EventHandler<CustomEventArgs> customSecondEvent和来自定义两个custom Event事件,它们的事件参数为CustomEventArgs.在窗体加载事件中我们触发两个事件(这个顺序会影响在窗体加载时订阅者的事件响应顺序.如果我们创建一个窗体继承此FormPublisher的话,我们会在此窗体的事件面板中看到下图:

 1 using System;  2 using System.Collections.Generic;  3 using System.ComponentModel;  4 using System.Data;  5 using System.Drawing;  6 using System.Linq;  7 using System.Text;  8 using System.Windows.Forms;  9 
10 namespace CustomEventsDemo 11 { 12     public partial class FormPublisher : Form 13  { 14         //定义两个事件
15         public event EventHandler<CustomEventArgs> customEvent; 16         public event EventHandler<CustomEventArgs> customSecondEvent; 17         public FormPublisher() 18  { 19  InitializeComponent(); 20  } 21 
22         private void FormWithCutomEvent_Load(object sender, EventArgs e) 23  { 24             //确定自定义事件的执行顺序,继承此窗体的子类窗体加载时的默认顺序
25             if (customEvent != null) 26  { 27                 CustomEventArgs customEventArgs = new CustomEventArgs(this.textBox1.Text, "customEvent"); 28                 customEvent(this, customEventArgs); 29  } 30             if (customSecondEvent != null) 31  { 32 
33                 CustomEventArgs customEventArgs = new CustomEventArgs(this.textBox1.Text, "customSecondEvent"); 34                 customSecondEvent(this, customEventArgs); 35  } 36 
37  } 38 
39         private void button1_Click(object sender, EventArgs e) 40  { 41             
42             this.textBox2.AppendText(this.textBox1.Text + "\r\n"); 43             //this.textBox1.Text = ""; 44             if (customSecondEvent != null) 45  { 46                 CustomEventArgs customEventArgs = new CustomEventArgs(this.textBox1.Text, "customSecondEvent"); 47                 //触发事件
48                 customSecondEvent(this, customEventArgs); 49  } 50             if (customEvent != null) 51  { 52                 CustomEventArgs customEventArgs = new CustomEventArgs(this.textBox1.Text, "customEvent"); 53                 //触发事件
54                 customEvent(this, customEventArgs); 55  } 56  } 57  } 58 }

3 订阅事件

　　下面定义一个FormSubscriber窗体来订阅自定义事件,我们要定义另一个窗体的事件,必须要先实例化那个窗体,否则会调用失败:

 1 using System;  2 using System.Collections.Generic;  3 using System.ComponentModel;  4 using System.Data;  5 using System.Drawing;  6 using System.Linq;  7 using System.Text;  8 using System.Windows.Forms;  9 
10 namespace CustomEventsDemo 11 { 12     public partial class FormSubscriber : Form 13  { 14         FormPublisher form = null; 15        public FormSubscriber() 16  { 17  InitializeComponent(); 18             //启动2个窗体
19             form = new FormPublisher(); 20             form.Visible = true; 21            //订阅事件
22             form.customSecondEvent += form_customSecondEvent; 23            //订阅事件
24             form.customEvent += form_customEvent; 25            //把发布窗体实例化后传入第二个订阅窗体中,否则不能订阅
26             FormSubScriber2 from2 = new FormSubScriber2(form); 27             from2.Visible = true; 28  } 29 
30        void form_customSecondEvent(object sender, CustomEventArgs e) 31  { 32            this.textBox1.AppendText("Message from Publisher " + e.Message + " from " + e.Tag + "\r\n"); 33  } 34 
35        void form_customEvent(object sender, CustomEventArgs e) 36  { 37            this.textBox1.AppendText("Message from Publisher " + e.Message + " from " + e.Tag + "\r\n"); 38  } 39 
40         private void FormSubscriber_Load(object sender, EventArgs e) 41  { 42             
43  } 44  } 45 }

 　　另一个窗体也进行订阅:

 1 using System;  2 using System.Collections.Generic;  3 using System.ComponentModel;  4 using System.Data;  5 using System.Drawing;  6 using System.Linq;  7 using System.Text;  8 using System.Windows.Forms;  9 
10 namespace CustomEventsDemo 11 { 12     public partial class FormSubScriber2 : Form 13  { 14      
15         public FormSubScriber2() 16  { 17  InitializeComponent(); 18  } 19         public FormSubScriber2(FormPublisher form) 20  { 21  InitializeComponent(); 22             //订阅form自定义事件
23             form.customEvent += form_customEvent; 24  } 25         void form_customEvent(object sender, CustomEventArgs e) 26  { 27             this.textBox1.AppendText("Message from Publisher " + e.Message + " from " + e.Tag + "\r\n"); 28  } 29 
30         private void FormSubScriber2_Load(object sender, EventArgs e) 31  { 32 
33  } 34  } 35 }