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) :
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 }
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 }
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 }