title: Sorting CollectionViewSource using custom IComparer
body: <p>I'm trying to sort a collection derived from CollectionViewSource, which simply has SortDescriptions for sorting. Unfortunately I need to be able to use my own custom IComparer, but I can't seem to find a way to do that. Think of a datagrid and I have my own multi-column sort algorithm. I'm thinking one way to do it is to use a collection implementing CollectionChanged that is an additional layer between the CollectionViewSource and my true datasource, but I would really prefer a better way if anyone has any suggestions.</p>