Setup infinite scrolling for windows store with gridview

binding.xaml

<GridView Grid.Row="1"  ItemsSource="{Binding Popular}" />

infiniteScrollingCollection.cs

    public class ScrollableObservableCollection : ObservableCollection<ApiSong>, ISupportIncrementalLoading
    {
        public ScrollableObservableCollection(IEnumerable<ApiSong> songs) : base(songs)
        {
            HasMoreItems = true;
        }
        public bool HasMoreItems { get; set; }
        private bool isRunning = false;
        public Windows.Foundation.IAsyncOperation<LoadMoreItemsResult> LoadMoreItemsAsync(uint count)
        {
            if (isRunning) //not thread safe
            {
                throw new InvalidOperationException("Only one operation in flight at a time");
            }
            isRunning = true;

            return AsyncInfo.Run(async c => {
                var api = App.container.Resolve<ApiMan>();
                var url = this.Last().PlaylistUrl;

                var currentPageNum = GetCurrentPageNumber(url);

                var songs = new ObservableCollection<ApiSong>();
                try
                {
                    songs = await api.GetSongs(url, "", 45, currentPageNum);                 
                }
                catch
                {
                    HasMoreItems = false;
                }

                foreach (var s in songs)
                {
                    if (!this.Any(x => x.itemid == s.itemid))
                    {
                        this.Add(s);
                    }
                    else
                    {
                        Debug.WriteLine("avoiding duplicate");
                    }
                }
 
                HasMoreItems = songs.Any();
                isRunning = false;
                return new LoadMoreItemsResult() {
                    Count = (uint)songs.Count
                };

            });
        }
    }

viewmodel.cs

namespace HypeM8.ViewModels
{
    class MoreViewmodel
    {
        private string _playlistUrl;
        public MoreViewmodel(string playlistUrl, string title)
        {
            _playlistUrl = playlistUrl;
            Popular = new ScrollableObservableCollection(GetItems());
        }

        private ObservableCollection<ApiSong> _popular;

        public ObservableCollection<ApiSong> Popular
        {
            get { return _popular; }
            set { _popular = value; NotifyPropertyChanged(); }
        }
        
    }
}