This interface defines an event consumer interface. The contract of the
of a consumer is to accept the event. This interface can be used to
mark an object as able to receive events. Add may be called several
times in immediate succession so a consumer must be able to cache
events it hasn't processed yet.
This method adds an event to the consumer. Calling this method
invalidates the event parameter. The client application should
discard all references to this event upon calling add.
The behavior of an application that continues to use such references