private void Button_Add_Event(object sender, RoutedEventArgs e)
        {
            AddGadget window = new AddGadget();

            window.ShowDialog();
            if (window.myGadget != null)
            {
                GadgetItems.Add(window.myGadget);
            }
        }
        private void AddGadget_Click(object sender, RoutedEventArgs e)
        {
            var gadgetWindow = new AddGadget();
            var dialog       = gadgetWindow.ShowDialog();

            if (dialog == true)
            {
                Console.WriteLine("Neues Gadget erfasst");
            }
            else
            {
                Console.WriteLine("Alles ist abgebrochen");
            }
        }