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using System;
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using System.ComponentModel;
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using System.Windows.Forms;
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namespace WindowsFormsApplication1
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{
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public partial class Form1 : Form
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{
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public delegate void ActionEventHandler(object sender, ActionCancelEventArgs ev);//声明一个delegate
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public static event ActionEventHandler Action;//声明一个名为Action的事件
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string _time = "";
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public Form1()
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{
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InitializeComponent();
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Form1.Action += new ActionEventHandler(Form1_Action);//为事件Action增加处理程序(即通过ActionEventHandler这个delegate来调用Form1_Action)
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}
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private void Form1_Action(object sender, ActionCancelEventArgs ev) //这里的方法签名必须与ActionEventHandler的声明签名相同
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{
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ev.Cancel = DoAction();//调用DoAction,根据当前时间是否超过30秒,决定是否取消事件(小于30秒取消,反之继续)
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if (ev.Cancel)
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{
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ev.Message = "当前时间小于30秒,事件被取消"; //如果取消,设置ev的Message属性
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}
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}
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/// <summary>
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/// 判断当前时间是否超过30秒
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/// </summary>
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/// <returns>小于30秒,返回true,反之返回false</returns>
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private bool DoAction()
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{
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bool retVal = false;
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DateTime tm = DateTime.Now;
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if (tm.Second < 30)
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{
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_time = "";
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retVal = true;
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}
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else
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{
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_time = "事件被触发于 " + DateTime.Now.ToLongTimeString();
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}
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return retVal;
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}
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/// <summary>
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/// 声明一个当前时间的属性
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/// </summary>
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public string TimeString
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{
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get { return _time; }
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}
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protected void OnAction(object sender, ActionCancelEventArgs ev)
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{
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if (Action!=null)//如果有人订阅了Action事件
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{
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Action(sender, ev);//则事件触发
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}
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}
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/// <summary>
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/// 通过按钮来激发事件
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/// </summary>
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/// <param name="sender"></param>
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/// <param name="e"></param>
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private void btnRaise_Click(object sender, EventArgs e)
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{
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ActionCancelEventArgs cancelEvent = new ActionCancelEventArgs();//生成一个ActionCancelEventArgs的实例
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OnAction(this, cancelEvent);//激发事件
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if (cancelEvent.Cancel)//如果事件被取消,则显示Message
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{
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lblInfo.Text = cancelEvent.Message;
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}
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else//反之显示当前时间
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{
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lblInfo.Text = this.TimeString;
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}
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}
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}
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public class ActionCancelEventArgs: CancelEventArgs
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{
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string _msg = "";
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//定义一个Message属性
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public string Message
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{
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get { return _msg; }
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set { _msg = value;}
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}
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}
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}
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