Following type used as ItemsSource doesn't display any items:

public class Test<T> : IEnumerable<T>, IEnumerable
{
private IEnumerable<T> _source;
public Test(IEnumerable<T> collection)
{
_source = collection.ToArray();
}
public IEnumerator<T> GetEnumerator()
{
return _source.GetEnumerator();
}
IEnumerator IEnumerable.GetEnumerator()
{
return GetEnumerator();
}
}

In WPF ItemsControl may accept any IEnumerable types.
I've tested in Unity only, but probably this relates to other environments too.
Also, this could be related to https://www.noesisengine.com/bugs/view.php?id=1017