Assembly: System.Web (in System.Web.dll)
The GridView control raises the PageIndexChanging event when a pager button (a button with its CommandName property set to "Page") within the control is clicked, but before the GridView control handles the paging operation. This allows you to provide an event-handling method that performs a custom routine, such as canceling the paging operation, whenever this event occurs.
Pager buttons are usually located in the pager row of a GridView control.
When you create a delegate, you identify the method that will handle the event. To associate the event with your event handler, add an instance of the delegate to the event. The event handler is called whenever the event occurs, unless you remove the delegate. For more information about event-handler delegates, see Events and Delegates.