List <ObservableCollection<TodoItem>> allTodoItemsLists= new List <ObservableCollection<TodoItem>>(); private ObservableCollection<TodoItem> selectedtodoItems; public ObservableCollection<TodoItem> SelectedTodoItems { get => selectedtodoItems; set { selectedtodoItems = value; OnPropertyChanged(); } } int currentListIndex; public int CurrentListIndex { get => currentListIndex; set{ currentListIndex=value; SelectedTodoItems = allTodoItemsLists[currentListIndex]; } }