试图从后台线程更新UI：为什么有时会抛出，有时什么也不做？

I've noticed in WPF that when trying to update the UI from a background thread (I know that you're not supposed to do this - just playing around with things) that sometimes it throws an InvalidOperationException, and sometimes it just does nothing. I first noticed this when I was improperly trying to update the UI from a background thread started by an async WCF call (using Begin/End, not the eventing model that automatically marshals to the UI thread).I've noticed in WPF that when trying to update