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<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="Default_aspx" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>HiddenField Control</title>
</head>
<script language=javascript>
function ChangeHiddenValue()
{
alert('Entering ChangeHiddenValue');
var hdnId = '<%=hdnSecretValue.ClientID%>'
var hdn = document.getElementById(hdnId);
var txt = document.getElementById('txtSecretValue');
hdn.value = txt.value;
alert('Value changed');
}
</script>
<body>
<form id="form1" runat="server">
<div>
<h1>HiddenField Control</h1>
<h2>This page was posted at <% =DateTime.Now.ToString() %>.</h2>
<asp:HiddenField ID="hdnSecretValue" runat="server" OnValueChanged="hdnSecretValue_ValueChanged" />
Enter secret value:
<asp:TextBox ID="txtSecretValue" runat="server" />
<br />
<br />
<input type=button value="Change hidden value" onclick="ChangeHiddenValue()" />
<asp:Button ID="btnPost" runat="server" Text="Post" />
<br />
<br />
<asp:Label ID="lblMessage" runat="server" Text=""/>
</div>
</form>
</body>
</html>
File: Default.aspx.cs
using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class Default_aspx : System.Web.UI.Page
{
protected void hdnSecretValue_ValueChanged(object sender, EventArgs e)
{
HiddenField hdn = (HiddenField)sender;
lblMessage.Text = "The new value is " + hdn.Value + ".";
}
}
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