Why can't I use LINQ on ListView.SelectedItems?

Question

I am trying to do use .Select extension method on ListView.SelectedItems which is SelectedListViewItemCollection, but .Select doesn't show up in intellisense.

I can use foreach on SelectedListViewItemCollection, so it must have implemented IEnumerable. I just checked on MSDN, and it certainly does. Then why can't the LINQ extension methods be used on it?

Answer 1

The reason why is that SelectedItems is typed to a collection which implements IEnumerable. The Select extension method is bound to IEnumerable<T>. Hence it won't work with SelectedItems.

The workaround is to use the .Cast extension method to get it to the appropriate type and it should show up

ListView.SelectedItems.Cast<SomeType>.Select(...)

Answer 2

It implements IEnumerable, not IEnumerable<T> - all LINQ queries are built around the generic IEnumerable<T> interface to allow type safety and generic inference - particularly when dealing with anonymous types.

You can use the following instead:

myListView.SelectedItems.Cast<ListViewItem>.Select( ... );

Answer 3

Do you have "using System.Linq" at the top of your file?

Is it a strongly typed generic collection? If not, you'll need to use the Cast<> extension method.