Custom event argument class which is used to signal a change in an element contained in the sender or in one of the elements contained (indirectly) in the sender, or an element was added to a collection contained in the sender or in one of the elements contained (indirectly) in the sender, or an element was removed from a collection contained in the sender or in one of the elements contained (indirectly) in the sender. The type of action (change, delete, addition) is determinable from the event, as there is one event per action.