observableItems.cs

   public class ObservableItems<T> : INotifyPropertyChanged
    {
        private IEnumerable<T> _items;

        public ObservableItems(IObservable<IEnumerable<T>> source, IEnumerable<T> initialValue)
        {
            Items = initialValue;
            source
                .ObserveOnDispatcher()
                .Subscribe(x => Items = x);
        }

        public IEnumerable<T> Items
        {
            get { return _items; }
            private set { _items = value; OnPropertyChanged(); }
        }

        public event PropertyChangedEventHandler PropertyChanged;

        protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
        {
            var handler = PropertyChanged;
            if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }