entity framework - C# unit of work bad implementation -

i tried implement unit of work sqlce database. works correctly except 1 thing.

i have scenario patient can perform different sessions , each session based on specific test. these implementations:

public class patient {     public int id { get; set; }     public byte[] identificationcode { get; set; }     public string sex { get; set; }      public virtual list<session> sessions { get; set; }         }  public class session {     public int id { get; set; }      public guid unique { get; set; }     public datetime datetime { get; set; }      public virtual patient patient { get; set; }     public virtual test test { get; set; }      public virtual list<videoexerciseresult> videosessionresults { get; set; }     public virtual list<audioexerciseresult> audiosessionresults { get; set; } }  public class test {     public int id { get; set; }     public string name { get; set; }      public virtual list<session> sessions { get; set; } } 

when perform test data saved , can directly go see results session.

but when run again application , load session results , test in session appear null (while patient, id , unique have correct values).

private void getsessiondata()     {         // list<test> templist = new list<test>(uow.tests.getall());         // list<audioexerciseresult> templist1 = new list<audioexerciseresult>(uow.audiosessionsresults.getall());          switch (selectedsession.test.name)         { 

and discovered loading list of tests , results database before calling session object make values of test , results inside session object correctly appear.

there don't understand in world of db. can clarify me why have load list of values db?

is wasn't clear explain more precisely...