Data for property events
The event.PropertyEvent class defines the data objects passed to listeners of the meta.property events:
event.PropertyEvent is a sealed subclass of event.EventData (i.e., you cannot subclass event.PropertyEvent).
event.PropertyEvent inherits the first two properties from the event.EventData, and defines one new property:
EventName — One of the four event names listed in the Description section
Source — meta.property object that triggers the event
AffectedObject — The object whose property is affected.