比如我们在页面上有3个TextBox，3个Button，每个Button分别执行不同的动作。我们现在想在TextBox中检测是否按下了回车键，如果是则执行不同的Button调用。即TextBox1中按下回车就执行Button1的动作,......
<%@ Page language="c#" Codebehind="WebForm2.aspx.cs" AutoEventWireup="false" Inherits="UTF8Test.WebForm2" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<HTML>
<HEAD>
<title>WebForm2</title>
<meta content="Microsoft Visual Studio .NET 7.1" name="GENERATOR">
<meta content="C#" name="CODE_LANGUAGE">
<meta content="javascript" name="vs_defaultClientScript">
<meta content="http://schemas.microsoft.com/intellisense/ie5"; name="vs_targetSchema">
<script language="javascript" event="onkeydown" for="TextBox1">
if(event.keyCode==13)<!-- 注意大小写-->
{
__doPostBack('Button1','');
return false;<!--很重要，不然会选择Button1进行提交 -->
}
</script>
<script language="javascript" event="onkeydown" for="TextBox2">
if(event.keyCode==13)
{
__doPostBack('Button2','');
return false;<!--很重要，不然会选择Button1进行提交 -->
}
</script>
<script language="javascript">
function keypress()
{
if(event.keyCode==13)
{
__doPostBack('Button3','');
event.keyCode=0; <!--很重要，不然会选择Button1进行提交 -->
return false;<!--很重要，不然会选择Button1进行提交 -->
}
}
</script>
</HEAD>
<body MS_POSITIONING="GridLayout">
<form id="Form1" method="post" runat="server">
<input type="hidden" name="__EVENTTARGET"> <input type="hidden" name="__EVENTARGUMENT">
<script language="javascript" type="text/javascript">
<!--
function __doPostBack(eventTarget, eventArgument) {
var theform;
if (window.navigator.appName.toLowerCase().indexOf("microsoft") > -1) {
theform = document.Form1;
}
else {
theform = document.forms["Form1"];
}
theform.__EVENTTARGET.value = eventTarget.split("$").join(":");
theform.__EVENTARGUMENT.value = eventArgument;
theform.submit();
}
// -->
</script>
<asp:button id="Button1" style="Z-INDEX: 101; LEFT: 192px; POSITION: absolute; TOP: 88px" runat="server"
Text="Button1"></asp:button><asp:textbox id="TextBox1" style="Z-INDEX: 102; LEFT: 16px; POSITION: absolute; TOP: 88px" runat="server"></asp:textbox>
<asp:Button id="Button2" style="Z-INDEX: 103; LEFT: 192px; POSITION: absolute; TOP: 120px" runat="server"
Text="Button2"></asp:Button>
<asp:TextBox id="TextBox2" style="Z-INDEX: 104; LEFT: 16px; POSITION: absolute; TOP: 120px" runat="server"></asp:TextBox>
<asp:TextBox id="TextBox3" style="Z-INDEX: 105; LEFT: 16px; POSITION: absolute; TOP: 152px" runat="server"></asp:TextBox>
<asp:Button id="Button3" style="Z-INDEX: 106; LEFT: 192px; POSITION: absolute; TOP: 152px" runat="server"
Text="Button3"></asp:Button>
<asp:Label id="Label1" style="Z-INDEX: 107; LEFT: 24px; POSITION: absolute; TOP: 56px" runat="server"></asp:Label></form>
</body>
</HTML>
WebForm2.aspx.cs
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using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;
namespace UTF8Test
{
/// <summary>
/// WebForm2 的摘要说明。
/// </summary>
public class WebForm2 : System.Web.UI.Page
{
protected System.Web.UI.WebControls.TextBox TextBox1;
protected System.Web.UI.WebControls.Button Button2;
protected System.Web.UI.WebControls.TextBox TextBox2;
protected System.Web.UI.WebControls.TextBox TextBox3;
protected System.Web.UI.WebControls.Button Button3;
protected System.Web.UI.WebControls.Label Label1;
protected System.Web.UI.WebControls.Button Button1;
private void Page_Load(object sender, System.EventArgs e)
{
// 在此处放置用户代码以初始化页面
TextBox3.Attributes.Add("onkeypress","keypress()");//注意大小写
}
Web 窗体设计器生成的代码
private void Button1_Click(object sender, System.EventArgs e)
{
Label1.Text = "1";
}
private void Button2_Click(object sender, System.EventArgs e)
{
Label1.Text = "2";
}
private void Button3_Click(object sender, System.EventArgs e)
{
Label1.Text = "3";
}
}
}
测试中，我发现要调用服务器端代码必须调用__doPostBack函数，但该函数除了在放置有DataGrid控件的页面中会由系统产生外，其他的页面中并不存在。（可以通过查看源文件看到该代码）。这样我们必须手工在aspx中添加__doPostBack函数，和函数一起添加的还有两个隐藏元素，__EVENTTARGET和__EVENTARGUMENT，这是__doPostBack所必须的，实际上，.NET是把产生事件的元素名称以及参数传到，__EVENTTARGET和__EVENTARGUMENT。然后再调用Form的submit函数提交回服务器的，服务器端根据传回来的参数就知道是哪个控件被触发了，从而调用它的相应后端代码，然后再将新页面回送回客户端的。
以下是我的测试页面，其中使用了两种方法来检测TextBox中的按键
WebForm2.aspx
--------------------------------------------------------
<%@ Page language="c#" Codebehind="WebForm2.aspx.cs" AutoEventWireup="false" Inherits="UTF8Test.WebForm2" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" ><HTML> <HEAD> <title>WebForm2</title> <meta content="Microsoft Visual Studio .NET 7.1" name="GENERATOR"> <meta content="C#" name="CODE_LANGUAGE"> <meta content="javascript" name="vs_defaultClientScript"> <meta content="http://schemas.microsoft.com/intellisense/ie5"; name="vs_targetSchema"> <script language="javascript" event="onkeydown" for="TextBox1"> if(event.keyCode==13)<!-- 注意大小写--> { __doPostBack('Button1',''); return false;<!--很重要，不然会选择Button1进行提交 --> } </script> <script language="javascript" event="onkeydown" for="TextBox2"> if(event.keyCode==13) { __doPostBack('Button2',''); return false;<!--很重要，不然会选择Button1进行提交 --> } </script> <script language="javascript"> function keypress() { if(event.keyCode==13) { __doPostBack('Button3',''); event.keyCode=0; <!--很重要，不然会选择Button1进行提交 --> return false;<!--很重要，不然会选择Button1进行提交 --> } } </script> </HEAD> <body MS_POSITIONING="GridLayout"> <form id="Form1" method="post" runat="server"> <input type="hidden" name="__EVENTTARGET"> <input type="hidden" name="__EVENTARGUMENT"> <script language="javascript" type="text/javascript"><!-- function __doPostBack(eventTarget, eventArgument) { var theform; if (window.navigator.appName.toLowerCase().indexOf("microsoft") > -1) { theform = document.Form1; } else { theform = document.forms["Form1"]; } theform.__EVENTTARGET.value = eventTarget.split("$").join(":"); theform.__EVENTARGUMENT.value = eventArgument; theform.submit(); }// --> </script> <asp:button id="Button1" style="Z-INDEX: 101; LEFT: 192px; POSITION: absolute; TOP: 88px" runat="server" Text="Button1"></asp:button><asp:textbox id="TextBox1" style="Z-INDEX: 102; LEFT: 16px; POSITION: absolute; TOP: 88px" runat="server"></asp:textbox> <asp:Button id="Button2" style="Z-INDEX: 103; LEFT: 192px; POSITION: absolute; TOP: 120px" runat="server" Text="Button2"></asp:Button> <asp:TextBox id="TextBox2" style="Z-INDEX: 104; LEFT: 16px; POSITION: absolute; TOP: 120px" runat="server"></asp:TextBox> <asp:TextBox id="TextBox3" style="Z-INDEX: 105; LEFT: 16px; POSITION: absolute; TOP: 152px" runat="server"></asp:TextBox> <asp:Button id="Button3" style="Z-INDEX: 106; LEFT: 192px; POSITION: absolute; TOP: 152px" runat="server" Text="Button3"></asp:Button> <asp:Label id="Label1" style="Z-INDEX: 107; LEFT: 24px; POSITION: absolute; TOP: 56px" runat="server"></asp:Label></form> </body></HTML>WebForm2.aspx.cs
----------------------------------------------------------------------
using System;using System.Collections;using System.ComponentModel;using System.Data;using System.Drawing;using System.Web;using System.Web.SessionState;using System.Web.UI;using System.Web.UI.WebControls;using System.Web.UI.HtmlControls;namespace UTF8Test{ /// <summary> /// WebForm2 的摘要说明。 /// </summary> public class WebForm2 : System.Web.UI.Page { protected System.Web.UI.WebControls.TextBox TextBox1; protected System.Web.UI.WebControls.Button Button2; protected System.Web.UI.WebControls.TextBox TextBox2; protected System.Web.UI.WebControls.TextBox TextBox3; protected System.Web.UI.WebControls.Button Button3; protected System.Web.UI.WebControls.Label Label1; protected System.Web.UI.WebControls.Button Button1; private void Page_Load(object sender, System.EventArgs e) { // 在此处放置用户代码以初始化页面 TextBox3.Attributes.Add("onkeypress","keypress()");//注意大小写 } Web 窗体设计器生成的代码 private void Button1_Click(object sender, System.EventArgs e) { Label1.Text = "1"; } private void Button2_Click(object sender, System.EventArgs e) { Label1.Text = "2"; } private void Button3_Click(object sender, System.EventArgs e) { Label1.Text = "3"; } }}
