public void btnAddGadget_Click(object sender, RoutedEventArgs e)
        {
            Gadget_hinzufügen window = new Gadget_hinzufügen();

            if (window.ShowDialog() == true)
            {
                mainWindow = (MainWindow)Window.GetWindow(this.Parent);
                // Update DataGrid
                mainWindow.RefreshDataGrid();
            }
        }
        public void btnAddGadget_Click(object sender, RoutedEventArgs e)
        {
            Gadget_hinzufügen window = new Gadget_hinzufügen();
            if (window.ShowDialog() == true)
            {
                mainWindow = (MainWindow)Window.GetWindow(this.Parent);
                // Update DataGrid
                mainWindow.RefreshDataGrid();

            }
        }