An EventFormatter is created either from an Event obtained from Service.CreatePublishEvent() or from Service.CreateResponseEvent(). Once one or more Messages have been appended to the Event using the EventFormatter the Event can be published using ProviderSession.Publish(Event)} or sent back as a response using ProviderSession.SendResponse(Event).

EventFormatter objects cannot be copied or assigned so as to ensure there is no ambiguity about what happens if two EventFormatters are both formatting the same Event.

The EventFormatter supports write once only to each field. It is an error to call SetElement() or PushElement() for the same name more than once at a particular level of the schema when creating a message.