The ItemUpdating event is raised when an item's Update button is clicked or the UpdateItem method is called,
The ItemUpdating event is raised when an item's Update button is clicked or the UpdateItem method is called, but before the ListView control updates the item. (An Update button is a button control whose CommandName property is set to "Update".) This enables you to perform a custom routine whenever this event occurs, such as canceling the update operation.
A ListViewUpdateEventArgs object is passed to the event handler, which enables you to determine the index of the current item. It also lets you indicate that the update operation should be canceled. To cancel the update operation, set the Cancel property of the ListViewUpdateEventArgs object to true.
You can work with the Keys, OldValues, and NewValues collections before the values are passed to the data source. A typical way to use these collections is to HTML-encode the values supplied by the user before they are stored in the data source. This helps prevent script injection attacks.