private async void BookPassengerButton_Click(object sender, RoutedEventArgs e)
        {
            string error = String.Empty;


            if (FirstName == String.Empty)
            {
                error += "First name can't be empty\n";
            }

            if (LastName == String.Empty)
            {
                error += "Last name can't be empty\n";
            }

            if (PhoneNumber == String.Empty)
            {
                error += "Phone Number can't be empty\n";
            }

            if (SelectedIndex == -1)
            {
                error += "You need to select a seat number\n";
            }

            if (error == String.Empty)
            {
                this.AllSeats = BookingViewModel.BookSeat(new Seat()
                {
                    FirstName   = FirstName,
                    LastName    = LastName,
                    Company     = Company,
                    PhoneNumber = PhoneNumber,
                    Number      = SelectedSeat.Number,
                    IsBooked    = true
                });

                var dialog = new MessageDialog(String.Format("Seat #{0} booked succesfully.", SelectedSeat.Number));
                await dialog.ShowAsync();

                this.Frame.GoBack();
            }
            else
            {
                var dialog = new MessageDialog(error);
                await dialog.ShowAsync();
            }
        }