Read XML and fetch records based on selected node using C# in ASP.Net

I have created an xml and have been able to call them nicely an populated them in imageButton and Labels using c#. i want to give the imageButton a PostBackUrl so that when you click on one of the imageButton, you will be redirect to another page with the information of that chosen item(ID). This is the class i used to call all the elements: 

public class XMLHelper
    {
        public List<CarClass> GetList()
        {
            XmlDocument xdoc = new XmlDocument();
            xdoc.Load(HttpContext.Current.Server.MapPath("~/advertenties.xml"));
            XmlNodeList AdvCars = xdoc.SelectNodes("/root/advertentie");
            var listOfAdStarCar = new List<CarClass>();
            if (AdvCars != null)
            {
                foreach (XmlNode AdvCar in AdvCars)
                {
                    var newAdStarCar = new CarClass();
                    //UnqNr

                    var unqNum = AdvCar.SelectSingleNode("unieknummer");
                    if (unqNum != null)
                    {
                        newAdStarCar.unqNr = Convert.ToInt32(unqNum.InnerText);
                    }

                    //lastMute
                    var lastMute = AdvCar.SelectSingleNode("laatstemutatie");
                    if (lastMute != null)
                    {
                        newAdStarCar.lastM = Convert.ToDateTime(lastMute.InnerText);
                    }

                    //name
                    var Dealername = AdvCar.SelectSingleNode("dealer/naam");
                    if (Dealername != null)
                    {
                        newAdStarCar.name = Dealername.InnerText;
                    }

                    //email
                    var E_mail = AdvCar.SelectSingleNode("dealer/email");
                    if (E_mail != null)
                    {
                        newAdStarCar.email = E_mail.InnerText;
                    }

                    //carNumber
                    var CarNummer = AdvCar.SelectSingleNode("auto/kenteken");
                    if (CarNummer != null)
                    {
                        newAdStarCar.CarNr = CarNummer.InnerText;
                    }

                    //company
                    var CarCompany = AdvCar.SelectSingleNode("auto/merk");
                    if (CarCompany != null)
                    {
                        newAdStarCar.CarCompany = CarCompany.InnerText;
                    }

                    //CarModel
                    var CarModel = AdvCar.SelectSingleNode("auto/model");
                    if (CarModel != null)
                    {
                        newAdStarCar.CarModel = CarModel.InnerText;
                    }

                    //BigImg
                    var FirstBigImage = AdvCar.SelectSingleNode("afbeeldingen/fotoGroot");
                    if (FirstBigImage != null)
                    {
                        newAdStarCar.BigImg = FirstBigImage.InnerText;
                    }

                    listOfAdStarCar.Add(newAdStarCar);
                }
            }
            return listOfAdStarCar;
        }

I've done this a couple of time with database, entity framework and there i did something like public class GetCar(int CarId){and here i will give somthing Find(CarId)} but I'm kind a stuck with XML 

I'm looking forward to your replies

Thanks in advance