private void Update_Click(object sender, RoutedEventArgs e)
        {
            var update = MessageBox.Show("Would you like to update the data??", "Update Data", MessageBoxButton.YesNo, MessageBoxImage.Question);

            if (update == MessageBoxResult.Yes)
            {
                passenger pas = new passenger(a.Count, int.Parse(custId_tb.Text), int.Parse(flightId_tb.Text));
                a[lpassenger.SelectedIndex] = pas;

                var pass = from upd in a
                           select upd.CustomerId;


                lpassenger.DataContext = pass;

                custId_tb.Clear();
                flightId_tb.Clear();

                MessageBox.Show("Details have been successfully Updated!!!", "Data Updated", MessageBoxButton.OK, MessageBoxImage.Information);
            }
        }
        public void Updatebtn_Click(object sender, RoutedEventArgs e)
        {
            if (custId_tb.Text == "" || flightId_tb.Text == "")
            {
                MessageBox.Show("All fields are required to update details", "Error", MessageBoxButton.OK, MessageBoxImage.Error);
            }
            else
            {
                var update = MessageBox.Show("Would you like to update the data??", "Update Data", MessageBoxButton.YesNo, MessageBoxImage.Question);
                if (update == MessageBoxResult.Yes)
                {
                    passenger pas1 = new passenger(a.Count, int.Parse(custId_tb.Text), int.Parse(flightId_tb.Text));
                    a[lpassenger.SelectedIndex] = pas1;

                    var pass = from up in a
                               select up.CustomerId;

                    lpassenger.DataContext = pass;
                    custId_tb.Clear();
                    flightId_tb.Clear();
                    MessageBox.Show("Details have been successfully Updated!!!", "Data Updated", MessageBoxButton.OK, MessageBoxImage.Information);
                }
            }
        }