private void btnDeleteCustomer_Click(object sender, RoutedEventArgs e)
        {
            facade.deleteCustomer(c);

            this.dataGridCustomer.ItemsSource = facade.getCustomersFromDataBase;
            this.dataGridCustomer.Items.Refresh();

            this.dataGridBooking.SelectedItem  = null;
            this.dataGridCustomer.SelectedItem = null;

            this.disableButtons();

            /*
             * data.deleteCustomer(c.CustomerReferenceNumber);
             *
             * customers.Remove(c);
             *
             * this.dataGridCustomer.ItemsSource = customers;
             * this.dataGridCustomer.Items.Refresh();
             *
             * this.dataGridCustomer.SelectedItem = null;
             * this.dataGridBooking.SelectedItem = null;
             *
             * this.disableButtons();
             */
        }