Thanks for the thoughts. You are right, the event is fired too early even though it appears after the various code required to 'load' the data. The GUI (this) is a user control and its main property dependency ActiveWell is synchronized with a property on an associated control. The associated control sets the ActiveWell property on this control. This control listens to its change property events and 'loads' the entity graph, as described above, and then fies another event. The control listens to its own events and attemps to get the collectioin for filtering..... So far so bad.