HiddenField In ASP.NET

<asp:HiddenFieldID="HiddenField1" runat="server" />  

ValueChanged event is server-side control. This event gets executed when the value of HiddenField gets changed between postback to the Server.

Nowadays, people avoid using server side ValueChanged Event because all these things are possible through JavaScript or jQuery very easily.

Store the value in HiddenField

<asp:HiddenFieldID="hdnfldCurrentDateTime" runat="server" />  

Set the value of HiddenField in code behind

protected void Page_Load(object sender, EventArgs e) {  
    hdnfldCurrentDateTime.Value = DateTime.Now.ToString();  
}

You can visit this article to see the right uses of HiddenField.

Retrieve the value from HiddenField

lblCurrentDateTime.Text = Convert.ToString(hdnfldCurrentDateTime.Value);

Step by step implementation

Create a new ASP.NET Website project called “HiddenFieldExample”.

Right click on project and select Add-->Add New Item and select Web Form.

Add a new Web Form called "Default.aspx".

Now, drag and drop the HiddenField Control on the page.

By default, the HiddenField control looks like this.

<asp:HiddenFieldID="HiddenField1" runat="server" />

Default.aspx Code

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>  
<!DOCTYP Ehtml>  
<html xmlns="http://www.w3.org/1999/xhtml">  
    <head runat="server">  
        <title></title>  
    </head>  
    <body>  
        <form id="form1" runat="server">  
             <div>  
                 <asp:HiddenFieldID="hdnfldCurrentDateTime" runat="server" />  
                 <asp:LabelID="lblCurrentDateTime" runat="server" Text=""></asp:Label>  
             </div>  
        </form>  
    </body>  
</html>

Default.aspx.cs Code

using System;    
using System.Collections.Generic;    
using System.Linq;    
using System.Web;    
using System.Web.UI;    
using System.Web.UI.WebControls;    
public partial class_Default: System.Web.UI.Page {    
    protected void Page_Load(object sender, EventArgs e) {    
        hdnfldCurrentDateTime.Value = DateTime.Now.ToString();    
        lblCurrentDateTime.Text = Convert.ToString(hdnfldCurrentDateTime.Value);    
    }    
}

Output

That's it. Happy Coding!!!