//edit the chosen booking
        private void btn_editbooking_Click(object sender, RoutedEventArgs e)
        {
            dynamic selected = lv_bookings.SelectedItem;

            //if no booking chosen then display error message
            if (selected == null)
            {
                MessageBox.Show("You haven't selected a booking to edit.");
                return;
            }

            int bref = 0;

            bref = selected.BookingRef;
            Booking booking   = bookingslist.Find(x => x.BookingRef == bref);
            var     newWindow = new BookingWindow(this, booking, customerlist);

            newWindow.ShowDialog();
        }
        //When the add booking button is pressed open an add booking window and  pass through the mainwindow and the customerlist
        private void btn_addbooking_Click(object sender, RoutedEventArgs e)
        {
            var newWindow = new BookingWindow(this, customerlist);

            newWindow.ShowDialog();
        }