Visual C#事件与接口编程实例

　　很多初学c#的朋友对于事件与接口感到迷惑不解，不明白它们之间的关系，下面我就用实例来简单的分析讲解一下。

　　事件，用event修饰符来代表一个事件，我们要创建一个C#事件必须按以下顺序来扫行：

　　1，创建或标识一个代表。比如下例中的

public delegate void dele(); //声明代表,delegate 关键字通知编译器 dele 是一个委托类型

　　2，创建一个包含事件处理代表，调用事件处理代表的方法的类，如下例

public class EventClass1 : IEvents //IEvents,是下面我们要讲一接口{public event dele event1;//定义事件成员event1public void FireEvent() //当事件发生时{event1(); //调用事件处理}}

　　EventClass1继承接口IEvents,以下后面的EventClass2~4，都是一样。

　　3，定义一个或多个把方法连接到事件的类

　　4，使用事件

　　4.1 定义事件响应方法,如下例中的

IEvents id1 = new EventClass1();

　　4.2 使用所定义的构造函数创建一个包含事件的对象,如下例中的

id1.event1 += new dele(EventFired1);

　　4.3 触发事件,如下例中的

id1.FireEvent();

　　下面我们来看看接口,我们必须用interface来声明一个接口。接口声明可以声明零个或多个成员。接口的成员必须是方法、属性、事件或索引器。接口不能包含常数、字段、运算符、实例构造函数、析构函数或类型，也不能包含任何种类的静态成员。

　　所有接口成员都隐式地具有 public 访问权限。接口成员声明包含任何修饰符属于编译时错误。具体地说，接口成员包含下列任何修饰符属于编译时错误：abstract、public、protected、internal、private、virtual、override 或 static。更多的信息请看msdn help://MS.VSCC/MS.MSDNVS.2052/csspec/html/vclrfcsharpspec_13_1.htm

　　在下面的例子中，我们声明IEvents接口，一个方法FireEvent和一个事件event1

public interface IEvents{event dele event1; //定义事件void FireEvent();//定义接口}

　　在后面的EventClass1~4类是继承了接口IEvent,因此在这几个类中必须实现上述一个方法和一个事件。下面的实例可以帮助大家更好的理解。

　　这是一个简单的windows Forms，包含一个textbox,几个labels和一个button,在程序启动时焦点在textbox,捕捉键盘按下事件，除方向键外,我能过接口来触事方向键按下事件。

　　下面的代码是一个网上常见的例程,大家可以拷贝下来，保存为.cs文件，用CSC编译就行

　　代码如下:

using System;using System.Drawing;using System.Collections;using System.ComponentModel;using System.Windows.Forms;using System.Data;namespace Events_Interfaces{public delegate void dele();//声明代表 delegate 关键字通知编译器 dele 是一个委托类型public interface IEvents //定义接口IEvents，包含方法FireEvent事件event1{event dele event1;void FireEvent();}public class Form1 : System.Windows.Forms.Form{private System.Windows.Forms.Label label1;private System.Windows.Forms.TextBox textBox1;private System.Windows.Forms.Label label2;private System.Windows.Forms.Button button1;private System.Windows.Forms.Label label3;private System.ComponentModel.Container components =null;public Form1(){InitializeComponent();}protected override void Dispose( bool disposing ){if( disposing ){if (components != null){components.Dispose();}}base.Dispose( disposing );}#region Windows Form Designer generated codeprivate void InitializeComponent(){this.textBox1 = new System.Windows.Forms.TextBox();this.label1 = new System.Windows.Forms.Label();this.button1 = new System.Windows.Forms.Button();this.label2 = new System.Windows.Forms.Label();this.label3 = new System.Windows.Forms.Label();this.SuspendLayout();this.textBox1.Location = new System.Drawing.Point(8, 80);this.textBox1.Name = "textBox1";this.textBox1.Size = new System.Drawing.Size(56,23);this.textBox1.TabIndex = 1;this.textBox1.Text = "";this.textBox1.KeyDown += new System.Windows.Forms.KeyEventHandler(this.Key_Press);this.label1.Location = new System.Drawing.Point(16, 16);this.label1.Name = "label1";this.label1.Size = new System.Drawing.Size(256,64);this.label1.TabIndex = 0;this.label1.Text = "Whenever you use the arrow keys inside the text box, Corresponding events will be" +"fired to display the label appropriately. Have a try!!";this.button1.Location = new System.Drawing.Point(240, 112);this.button1.Name = "button1";this.button1.Size = new System.Drawing.Size(48,23);this.button1.TabIndex = 3;this.button1.Text = "Exit";this.button1.Click += new System.EventHandler(this.button1_Click);//// label2//this.label2.Location = new System.Drawing.Point(88, 80);this.label2.Name = "label2";this.label2.Size = new System.Drawing.Size(184,23);this.label2.TabIndex = 2;this.label2.TextAlign =System.Drawing.ContentAlignment.MiddleCenter;//// label3//this.label3.Location = new System.Drawing.Point(8, 104);this.label3.Name = "label3";this.label3.Size = new System.Drawing.Size(64,23);this.label3.TabIndex = 4;this.label3.TextAlign =System.Drawing.ContentAlignment.MiddleCenter;//// Form1//this.AutoScaleBaseSize = new System.Drawing.Size(6, 16);this.ClientSize = new System.Drawing.Size(292,141);this.Controls.AddRange(new System.Windows.Forms.Control[] {this.label3,this.button1,this.label2,this.textBox1,this.label1});this.Font= new System.Drawing.Font("Comic SansMS",8.25F,System.Drawing.FontStyle.Regular,System.Drawing.GraphicsUnit.Point,((System.Byte)(0)));this.Name = "Form1";this.Text = "Events";this.ResumeLayout(false);}#endregionstatic void Main(){Application.Run(new Form1());}private void Key_Press(object sender,System.Windows.Forms.KeyEventArgs e){textBox1.Text = "";label2.Text = "";string keyId = e.KeyCode.ToString();switch (keyId)//判断是否按下方向键{case "Right":label3.Text = "";IEvents id1 = new EventClass1(); //实例化一个接口id1.event1 += new dele(EventFired1);//定义EventClass1中的事件响应方法id1.FireEvent();//调用EventClass1中的FireEvent方法，触发event1 事件，事件调用EventFired1方法break;case "Left":label3.Text = "";IEvents id2 = new EventClass2();id2.event1 += newdele(EventFired2);id2.FireEvent();break;case "Down":label3.Text = "";IEvents id3 = new EventClass3();id3.event1 += newdele(EventFired3);id3.FireEvent();break;case "Up":label3.Text = "";IEvents id4 = new EventClass4();id4.event1 += newdele(EventFired4);id4.FireEvent();break;default:label3.Text = keyId;break;}}//EventFired1方法public void EventFired1(){label2.Text = "";label2.Text = "You pressed RIGHT arrow key";}public void EventFired2(){label2.Text = "";label2.Text = "You pressed LEFT arrow key";}public void EventFired3(){label2.Text = "";label2.Text = "You pressed DOWN arrow key";}public void EventFired4(){label2.Text = "";label2.Text = "You pressed UP arrow key";}private void button1_Click(object sender,System.EventArgs e){Application.Exit();}}public class EventClass1 : IEvents{public event dele event1;public void FireEvent(){event1();}}public class EventClass2 : IEvents{public event dele event1;public void FireEvent(){event1();}}public class EventClass3 : IEvents{public event dele event1;public void FireEvent(){event1();}}public class EventClass4 : IEvents//EventClass1继承接口IEvents{public event dele event1;//定义事件成员event1//当事件发生时public void FireEvent(){event1();//调用事件处理}}}