public event EventHandler ClickEventHandler;??? protected void Button1_Click(object sender, EventArgs e)???? {???????? if (ClickEventHandler != null)???????? {???????????? ClickEventHandler(this, EventArgs.Empty);???????? }???? }問題1：請問這個事件ClickEventHandler什么都沒綁定，我想說的是：委托事件里連一個方法都沒有聲明和綁定，但我們點擊觸發(fā) Button1_Click時，此段代碼【???????? if (ClickEventHandler != null)???????? {???????????? ClickEventHandler(this, EventArgs.Empty);???????? }】如何運行啊,事件是點擊了botton1按鈕，什么反應(yīng)也沒有,在上下文中，究竟起了什么作用，這神來之筆，對于上下文究竟起什么作用，？？？？？不會做做樣子，可要可無的嗎，需要的這段代碼嗎？
問題2：?ClickEventHandler(this, EventArgs.Empty);怎么還有傳入空參數(shù)EventArgs.Empty啊，那不寫，就是傳入空參數(shù)，還是說EventArgs.Empty傳入的參數(shù)是有值的（下面還有個問題3，麻煩了）
注意：地處的代碼是創(chuàng)建（用戶控件）的關(guān)于委托事件的代碼完整的代碼如下? MyControl.ascx的代碼<%@ Control Language="C#" AutoEventWireup="true" CodeFile="MyControl.ascx.cs" Inherits="MyControl" %><asp:TextBox ID="TextBox1" runat="server" Width="193px">請輸入搜索內(nèi)容</asp:TextBox><asp:Button ID="Button1" runat="server" Text="搜索" onclick="Button1_Click" />MyControl.ascx.cs后置代碼using System;using System.Collections;using System.Configuration;using System.Data;using System.Linq;using System.Web;using System.Web.Security;using System.Web.UI;using System.Web.UI.HtmlControls;using System.Web.UI.WebControls;using System.Web.UI.WebControls.WebParts;using System.Xml.Linq;public partial class MyControl : System.Web.UI.UserControl{???? protected void Page_Load(object sender, EventArgs e)???? {???? }???? public string FindText???? {???????? get { return TextBox1.Text; }???????? set { TextBox1.Text = value; }???? }???? public event EventHandler ClickEventHandler;??? protected void Button1_Click(object sender, EventArgs e)???? {???????? if (ClickEventHandler != null)???????? {???????????? ClickEventHandler(this, EventArgs.Empty);???????? }???? }}
我用來測試UserMyControl.aspx的頁面代碼
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="UseLMyControl.aspx.cs" Inherits="UseLMyControl" %>
<%@ Register src="MyControl.ascx" tagname="MyControl" tagprefix="uc1" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server"> ???
<title>無標(biāo)題頁</title>
</head>
<body> ???
<form id="form1" runat="server"> ???
<div> ??? <uc1:MyControl ID="MyControl1" runat="server" OnClickEventHandler="MyControl1_Click"/> ?????
<br /> ??????? <asp:Label ID="Label1" runat="server" Text="什么情況"></asp:Label> ???
</div> ??
? </form>
</body>
</html>
UserMyControl.aspx.cs的后置代碼
using System; using System.Collections; using System.Configuration; using System.Data; using System.Linq; using System.Web; using System.Web.Security; using System.Web.UI; using System.Web.UI.HtmlControls; using System.Web.UI.WebControls; using System.Web.UI.WebControls.WebParts; using System.Xml.Linq;
public partial class UseLMyControl : System.Web.UI.Page
{ ??? protected void Page_Load(object sender, EventArgs e) ??
? {
??? } ???
public void MyControl1_Click(object sender, EventArgs e) ??
? { ??????? Label1.Text = MyControl1.FindText; ??? }
}
?
問題3：好像刪除了這段代碼
public event EventHandler ClickEventHandler;??? protected void Button1_Click(object sender, EventArgs e)???? {???????? if (ClickEventHandler != null)???????? {???????????? ClickEventHandler(this, EventArgs.Empty);???????? }???? }
也不行，請問什么原因，只要不刪除public event EventHandler ClickEventHandler;這一句有可以，、為什么?。?？？
這是一個教人如何使用用戶控件的列子，沒有其他代碼了，希望大家別把問題復(fù)雜化，我沒有其他代碼要交代，也不會有聲明在其他地方的可能
事件委托的，與他們的觸發(fā)關(guān)系，請求大家指導(dǎo)，在此謝過大家了
慕標(biāo)5832272
2018-12-06 22:38:27
