June CTP TreeView.ItemsSource no longer works with IEnumerable. Bug?

Question

I'm setting the ItemsSource on a TreeView controls like this:

public IEnumerable ItemsSource

{

      get

      {

            return treeView.ItemsSource;

      }

      set

      {

            treeView.ItemsSource = value;

      }

}

I'm pretty sure this was working in the May CTP, but now it doesn't work unless I do this:

public IEnumerable ItemsSource

{

      get

      {

            return treeView.ItemsSource;

      }

      set

      {

            ObservableCollection<object> theCollection = new ObservableCollection<object>();

            foreach (object item in value)

            {

                  theCollection.Add(item);

            }

 

            treeView.ItemsSource = theCollection;

      }

}

Looks like a bug.