HiddenField.ValueChanged Event
Definition
Important
Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.
Occurs when the value of the HiddenField control changes between posts to the server.
public:
event EventHandler ^ ValueChanged;public event EventHandler ValueChanged;member this.ValueChanged : EventHandler Public Custom Event ValueChanged As EventHandler Event Type
Examples
The following example demonstrates how to use the ValueChanged event to display the value of the HiddenField control.
Important
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>
<%@ Page language="VB" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
Sub ValueHiddenField_ValueChanged(ByVal sender As Object, ByVal e As EventArgs)
' Display the value of the HiddenField control.
Message.Text = "The value of the HiddenField control is " & ValueHiddenField.Value & "."
End Sub
</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>
Remarks
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 how to handle events, see Handling and Raising Events.
