private void HandleCreateListCommand(object parameter) { if (this.Title == null) { this.Message = "Title can not be null!"; return; } if (this.Todos.Count == 0) { this.Message = "Todo list must contain at least one !"; return; } var filledTodoes = this.Todos.Where(t => !string.IsNullOrEmpty(t.Text)); if (filledTodoes.Count() == 0) { this.Message = "Todo list must contain at least one Todo!"; return; } DataPersister.CreateNewTodosList(this.Title, filledTodoes); this.Title = ""; this.Todos.Clear(); this.TodoLists = DataPersister.GetTodoLists(); }