Following the email sample
that you've produced to show the Expander control, it uses an ExpderControl inside a RadDataBoundListBox which looks great out of the box.
When the bound list changes, the header in the ExpanderControl does not refresh/rebind. I've put together a sample application here
; which shows both changing the List entirely and also just clearing the list with new items. On the second page of the pivot control, the same items are bound to the build-in longlistselector which updates without problems.
The other behaviour I've noticed is that the Expander Control doesn't properly work in an ItemsControl or LongListSelector, as in, none of the items seem to bind properly, though this could be a separate issue.
My use case is: A user has done a search to view an initial list of items, and can then re-search with different parameters to return a completely different set of items.