Listview GroupHeaderTemplate

Is it possible to bind to a listview with classes like this? All examples of listview group headers have had the class something like :

public class Test : ObservableCollection<TestTwo>.

but I want my classes to look like this, is it possible? Right now Xamarin Forms can't find any of the properties on my class.

    public class Test 
    {
        public string ItemName { get; set; }

        public ObservableCollection<TestTwo> List { get; set; }

        public Test () {

            List = new ObservableCollection<TestTwo> ();

        }
    }

    public class TestTwo 
    {
        public string Count { get; set; }
    }