private void MenuItem_Click(object sender, RoutedEventArgs e)
        {
            Kırtasiye k = new Kırtasiye();

            this.NavigationService.Navigate(k);
        }
        private void Button_Click_6(object sender, RoutedEventArgs e)
        {
            Kırtasiye k = new Kırtasiye();

            this.NavigationService.Navigate(k);
        }