C#EntityFramework 5在插入时丢失引用

我有EF5，并希望（有…）建立一个多层应用程序。EF是我的持久层，我为我的客户使用WCF。现在我的业务逻辑有一个问题，我不能完全理解

我有一个方法，应该保留一些东西。当我使用.SaveChanges（）将预订发送到数据库时，一切都正常

public bool bReservieren(Student oStudent, Korb oKorb, IEnumerable<Service> lServices, DateTime dtFrom, DateTime dtTo)
    {
        try
        {
            BeachChaireModelContainer context = new BeachChaireModelContainer();

            Reservierung newReservation = context.Reservation.Create();
            //Tried it with newReservation.Student = oStudent; But there is an 
            //error cause of the different context´s so I search the correct Student
            //again. (same with Korb)
            newReservation.Student = context.Student.Find(oStudent.Kartennummer);
            newReservierung.Korb = context.Korb.Find(oKorb.KID);
            newReservierung.dtVON = dtFrom;
            newReservierung.dtBIS = dtTo;
            newReservierung = context.Reservation.Add(newReservation);
               //This if isnt relevant yet. lService is null in my tests     
               if (lServices != null)
               {
                  foreach (var item in lServices)
                  {
                     newReservation.Service.Add(context.Service.Find(item.SeID));
                  }
               }

               context.SaveChanges();
               return true;
        }
        catch (Exception)
        { }

        return false;
    }

我将Student和Korb属性设置为空值？数据库中的一切都是正确的。（存储了正确的外键）

有人知道这种行为吗

换句话说，当我尝试在另一个环境下再次获得预订时，我无法执行以下操作：

//had to mention it is a new Methode with a new context, but this should
//be no Problem in my oppinion? 
var query = from it in context.Reservation
            select it;

String test = newReservation.Student.Surename;

---

原因Student==null

您很可能启用了延迟加载（通过将

Student

属性设置为虚拟）。如果是这种情况，则从数据库加载时必须

包含（）

var query = from it in context.Reservation.Include("Student")
            select it;