public TodoListViewModel(IEnumerable <TodoItem> _items) { this.items = _items; // Items = new ReactiveList<TodoItem>(items); // CheckedItems = //Items = new ObservableCollection<TodoItem>(items); //CheckedItems = new ObservableCollection<TodoItem>( // Items.Where((todoItem) => todoItem.IsChecked) //); foreach (var item in Items) { item.Changed.Subscribe((model) => { CheckedItems.Clear(); CheckedItems.AddRange(Items.Where((todoItem) => todoItem.IsChecked)); }); } }