How update my list or add data to List

when i add data to additionalservicesnew list but not add data its null

here is my code

public class BookingDetailsData
{
public List LstbookingPassengerDetails { get; set; }
public List lstFlightDetail { get; set; }
public List golstFlightDetail { get; set; }
public List backlstFlightDetail { get; set; }
public List lstAdditionServiceDetails { get; set; }
public List lstAdditionServiceDetailsNew { get; set; }
public int TotalAmount { get; set; }
public double goFinalTotalAmount { get; set; }
public double backFinalTotalAmount { get; set; }
public int UserId { get; set; }
public double FinalTotalAmount { get; set; }

}






public class AdditionalServiceNew
{
    public int PaxSeqNo { get; set; }
    public string FromStationCode { get; set; }
    public string ToStationCode { get; set; }
    public string Type { get; set; }
    public double BaggageAmount { get; set; }
    public double MealAmount { get; set; }
    public string ServiceCode { get; set; }
    public string ServiceName { get; set; }
    public double Amount { get; set; }
    public double TotalAmount { get; set; }



}   

/// in cs file

on click confirmed i added additionalservices

List data1 = new List();

            //new codse meal
            AdditionalServiceNew additionalmeal = new AdditionalServiceNew();
            additionalmeal.Amount = Convert.ToDouble(bookingDetails.lstFlightDetail[0].TotalAmount);
            additionalmeal.MealAmount = Convert.ToDouble(subitemSelectedm.MealAmount);
            additionalmeal.Type = "Meal";
            additionalmeal.TotalAmount = bookingDetails.FinalTotalAmount;
            additionalmeal.PaxSeqNo = 1;
            additionalmeal.ServiceCode = subitemSelectedm.MealServiceCode;
            additionalmeal.ServiceName = subitemSelectedm.MealServiceName;






            //new codse baggage

            AdditionalServiceNew additionalbag = new AdditionalServiceNew();
            additionalbag.Amount = Convert.ToDouble(bookingDetails.lstFlightDetail[0].TotalAmount);
            additionalbag.MealAmount = Convert.ToDouble(subitemSelectedb.BaggageAmount);
            additionalbag.Type = "Baggage";
            additionalbag.TotalAmount = bookingDetails.FinalTotalAmount;
            additionalbag.PaxSeqNo = 1;
            additionalbag.ServiceCode = subitemSelectedb.BaggageServiceCode;
            additionalbag.ServiceName = subitemSelectedb.BaggageServiceCode;

            data1.Add(additionalbag);
            data1.Add(additionalmeal);

// this is my listview bookingDetails.lstAdditionsServicesDetailsNew not added data

bookingDetails.lstAdditionServiceDetailsNew.AddRange(data1);