Thank you, that is correct.  It makes sense now. BTW, another alternative is to set e.handled = true. 

LostFocus is a routed bubble event. So the first event you are seeing is when the focus is shifting to the child control. In that case the e.OriginalSource is probably the editor itself. When the child control is losing focus then the LostFocus for it bubbles up the visual/logical tree but in that case the e.OriginalSource is the child control.

Hi Stefan,  thank you for your answer.  I still do not understand why the event is fired twice.  If I understand the post you referenced correctly, the parent control fires LostFocus when it passes focus to the child.  That does not explain why LostFocus is raised again when the child control loses it.  In other words, I am binding to the lost focus event of exactly one control, whether it be child or parent.  Therefore I should receive notice of exactly one event.  Thats my .02 :)

Thank you,

Sam