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HiddenField.ValueChanged Event

Occurs when the value of the HiddenField control changes between posts to the server.

Namespace:  System.Web.UI.WebControls
Assembly:  System.Web (in System.Web.dll)

public event EventHandler ValueChanged

The ValueChanged event is raised when the value of the HiddenField control changes between posts to the server. This allows you to provide an event-handling method that performs a custom routine whenever this event occurs.

For more information about handling events, see Consuming Events.

The following example demonstrates how to use the ValueChanged event to display the value of the HiddenField control.

Security noteSecurity Note

This example has a text box that accepts user input, which is a potential security threat. By default, ASP.NET Web pages validate that user input does not include script or HTML elements. For more information, see Script Exploits Overview.


<%@ Page language="C#" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">

  void ValueHiddenField_ValueChanged (Object sender, EventArgs e)
  {

    // Display the value of the HiddenField control.
    Message.Text = "The value of the HiddenField control is " + ValueHiddenField.Value + ".";

  }

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
    <head runat="server">
    <title>HiddenField Example</title>
</head>
<body>
        <form id="Form1" runat="server">

            <h3>HiddenField Example</h3>

            Please enter a value and click the submit button.<br/>

            <asp:Textbox id="ValueTextBox"
              runat="server"/>

            <br/>  

            <input type="submit" name="SubmitButton"
             value="Submit"
             onclick="PageLoad()" />

            <br/>

            <asp:label id="Message" runat="server"/>    

            <asp:hiddenfield id="ValueHiddenField"
              onvaluechanged="ValueHiddenField_ValueChanged"
              value="" 
              runat="server"/>

        </form>
    </body>
</html>

<script type="text/javascript">

  <!--
  function PageLoad()
  {

    // Set the value of the HiddenField control with the
    // value from the TextBox.
    Form1.ValueHiddenField.value = Form1.ValueTextBox.value;

  }
  -->

</script>

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0
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