Xamarin Forms Collection View Multi-Selection Binding

I spent a few too many hours fiddling with Xamarin Form’s collection view and multi-selection binding. That was somewhat frustrating so I’m writing a little about it in the hopes that you don’t have to deal with the same.

If you have a view like this:

and a View Model like this:

You’d expect the binding to work, right? No problems. Well, no. It doesn’t. The CollectionView will only bind SelectedItems to collections of object. I don’t know why the Xamarin team decided to go that route, but it is a quirk that has wasted too many hours. While the view example above is correct, the View Model should look like this:

There is some info about this problem in this GitHub issue. Also, the quirk is expected to be fixed in .net5 as shown in this open PR.

Cheers, Lucas