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 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  
            //C#接口编程实例  
            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  
            //C#接口编程实例  
            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",
            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 += 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";
        }
        //C#接口编程实例  
        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();//C#接口编程实例之调用事件处理

}
    }

}