public MemorizationViewController() : base("Memorization") { verses = VersesTableViewController.Current.Verses; verses.CollectionChanged += delegate(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e) { if (tableView != null) { var newItems = e.NewItems; var oldItems = e.OldItems; if (newItems != null) { foreach (Verse verse in newItems) { if (verse.Category == categoryToFilter) { filteredVerses.Add(verse); Console.WriteLine(verse.Title); } } } if (oldItems != null) { foreach (Verse verse in oldItems) { if (filteredVerses.Any(item => item.Id == verse.Id)) { filteredVerses.Remove(verse); Console.WriteLine(verse.Title); } } } } }; }