Using the CollectionViewSource is a good way of binding to a datasource and letting the XAML determine the sorting and grouping of the data. However, as your datasource changes, the grouping and sorting is not automatically "re-calculated", forcing your code to be smarter that it should be. I found a
class today on MSDN forums that inherits from CollectionViewSource and adds automatic refresh capabilities. This code is smart enough to resort your items, regroup your items and even add new groupings as needed.
Some good CollectionViewSource links: