Assembly: System.Web (in system.web.dll)
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.
Raising an event invokes the event handler through a delegate. For more information, see Raising an Event.
The OnValueChanged method also allows derived classes to handle the event without attaching a delegate. This is the preferred technique for handling the event in a derived class.Notes to Inheritors: When overriding the OnValueChanged method in a derived class, be sure to call the base class’s OnValueChanged method so that registered delegates receive the event.