CollectionViewSource ... pre-set sort description is ignored

Hi,

consider the following situation:

I have a CollectionViewSource with a pre-set default sort description. This may be set right after constructing the instance of CollectionViewSource. Later on (e.g. using the "Loaded" Event) the source property is set. Now, the items are shown but not in sorted order. Only after changing the sort description the items get sorted. What am I missing ?

Greetings

Chris