private void UpdateBtn_Click(object sender, RoutedEventArgs e) { if (listView.SelectedValue == null) { MessageBox.Show("Please, select item to edit"); return; } NewTaskWindow modalWindow = new NewTaskWindow(); var selectedTask = (Task)listView.SelectedItem; modalWindow.EditTask = selectedTask; if (modalWindow.ShowDialog() == true) { listView.ItemsSource = TaskController.UpdateItem(selectedTask.Title, modalWindow.EditTask, selectedTask.Id); } }