It's a bit confusing that the SelectedItems Property in CollectionView only accepts IList<object> as type and you have to cast every single item in order to get those.

so why don't enhance it?

i've been using the free dxCollectionView from Devexpress and they seem to support it.
see here

Sample to reproduce the current behavior:
https://github.com/maslewandowski/bindingfailurecollectionview