CarouselView.ItemsSource.cs

public static readonly BindableProperty ItemsSourceProperty =
    BindableProperty.Create<CarouselLayout, IList> (
        view => view.ItemsSource,
        null,
        propertyChanging: (bindableObject, oldValue, newValue) => {
        ((CarouselLayout)bindableObject).ItemsSourceChanging ();
    },
        propertyChanged: (bindableObject, oldValue, newValue) => {
        ((CarouselLayout)bindableObject).ItemsSourceChanged ();
    }
    );

public IList ItemsSource {
    get {
        return (IList)GetValue (ItemsSourceProperty);
    }
    set {
        SetValue (ItemsSourceProperty, value);
    }
}

void ItemsSourceChanging ()
{
    if (ItemsSource == null) return;
    _selectedIndex = ItemsSource.IndexOf (SelectedItem);
}

void ItemsSourceChanged ()
{
    _stack.Children.Clear ();
    foreach (var item in ItemsSource) {
        var view = (View)ItemTemplate.CreateContent ();
        var bindableObject = view as BindableObject;
        if (bindableObject != null)
            bindableObject.BindingContext = item;
        _stack.Children.Add (view);
    }
    
    if (_selectedIndex >= 0) SelectedIndex = _selectedIndex;
}