很多初學c#的朋友對於事件與接口感到迷惑不解，不明白它們之間的關系，下面我就用實例來簡單的分析講解一下。
事件，用event修飾符來代表一個事件，我們要創建一個C#事件必須按以下順序來掃行：
1，創建或標識一個代表。比如下例中的
public delegate void dele(); //聲明代表,delegate 關鍵字通知編譯器 dele 是一個委托類型
2，創建一個包含事件處理代表，調用事件處理代表的方法的類，如下例
public class EventClass1 : IEvents //IEvents,是下面我們要講一接口
{
public event dele event1;//定義事件成員event1
public void FireEvent() //當事件發生時
{
event1(); //調用事件處理
}
}EventClass1繼承接口IEvents,以下後面的EventClass2~4，都是一樣。
3，定義一個或多個把方法連接到事件的類
4，使用事件
4.1 定義事件響應方法,如下例中的
IEvents id1 = new EventClass1();
4.2 使用所定義的構造函數創建一個包含事件的對象,如下例中的
id1.event1 += new dele(EventFired1);
4.3 觸發事件,如下例中的
id1.FireEvent();
下面我們來看看接口,我們必須用interface來聲明一個接口。接口聲明可以聲明零個或多個成員。接口的成員必須是方法、屬性、事件或索引器。接口不能包含常數、字段、運算符、實例構造函數、析構函數或類型，也不能包含任何種類的靜態成員。
所有接口成員都隱式地具有 public 訪問權限。接口成員聲明包含任何修飾符屬於編譯時錯誤。具體地說，接口成員包含下列任何修飾符屬於編譯時錯誤：abstract、public、protected、internal、private、virtual、override 或 static。更多的信息請看msdn help://MS.VSCC/MS.MSDNVS.2052/csspec/html/vclrfcsharpspec_13_1.htm
在下面的例子中，我們聲明IEvents接口，一個方法FireEvent和一個事件event1
public interface IEvents
{
event dele event1; //定義事件
void FireEvent();//定義接口
}在後面的EventClass1~4類是繼承了接口IEvent,因此在這幾個類中必須實現上述一個方法和一個事件。下面的實例可以幫助大家更好的理解。
這是一個簡單的windows Forms，包含一個textbox,幾個labels和一個button,在程序啟動時焦點在textbox,捕捉鍵盤按下事件，除方向鍵外,我能過接口來觸事方向鍵按下事件。
下面的代碼是一個網上常見的例程,大家可以拷貝下來，保存為.cs文件，用CSC編譯就行
代碼如下:
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();//聲明代表 delegate 關鍵字通知編譯器 dele 是一個委托類型
public interface IEvents //定義接口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 code
private 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);
}
#endregion
static 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)//判斷是否按下方向鍵
{
case "Right":
label3.Text = "";
IEvents id1 = new EventClass1(); //實例化一個接口
id1.event1 += new dele(EventFired1);//定義EventClass1中的事件響應方法
id1.FireEvent();//調用EventClass1中的FireEvent方法，觸發event1 事件，事件調用EventFired1方法
break;
case "Left":
label3.Text = "";
IEvents id2 = new EventClass2();
id2.event1 += new
dele(EventFired2);
id2.FireEvent();
break;
case "Down":
label3.Text = "";
IEvents id3 = new EventClass3();
id3.event1 += new
dele(EventFired3);
id3.FireEvent();
break;
case "Up":
label3.Text = "";
IEvents id4 = new EventClass4();
id4.event1 += new
dele(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繼承接口IEvents
{
public event dele event1;//定義事件成員event1
//當事件發生時
public void FireEvent()
{
event1();//調用事件處理
}
}
}
