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