nHibernate One to One property null when loaded - nhibernate

Question

I have a One to One relation between a TimeRecord and the Location.
This implementation is exactly the same es described in documentation:
https://github.com/jagregory/fluent-nhibernate/wiki/Fluent-mapping
public class TimeRecordMap : ClassMap<TimeRecord>
{
public TimeRecordMap()
{
Id(x => x.Id);
Map(x => x.Description);
Map(x => x.StartTime);
Map(x => x.EndTime);
HasOne(x => x.Location).Cascade.All();
}
}
public class LocationMap : ClassMap<Location>
{
public LocationMap()
{
Id(x => x.Id);
Map(x => x.Longitude);
Map(x => x.Latitude);
Map(x => x.Adress);
References(x => x.TimeRecord).Unique();
}
}
Now I query my TimeRecords with the following method:
public IList<TimeRecord> GetTimeRecords(string userid)
{
var query = Session.Query<TimeRecord>().Where(tr => tr.User.Id == userid);
return query.ToList();
}
Unfortunalelty my Location object is always null even if there is a coresponding entry in Location table but when I query for the coresponding Location with the desired TimeRecordId it is returned correctly.
See code here (code is inside a loop -> trCurrent is the current object in list received from "GetTimeRecords")
Location location = _locationRepo.getLocationByTimeRecordId(trCurrent.Id);
//trCurrent.Location = location; <- don't want to do it that way
if (trCurrent.Location != null)<- always null
{
... do stuff here
}
Implementation of my LocationRepository method:
public Location getLocationByTimeRecordId(int timeId)
{
var query = Session.Query<Location>()
.Where(tr => tr.TimeRecord.Id == timeId && tr.IsDeleted == false);
List<Location> lstReturn = query.ToList();
if (lstReturn.Count() == 0)
{
return null;
}
else
{
return lstReturn.First();
}
}
Can someone tell me why my Location is not resolved corretly?
Cheers,
Stefan

Answer 1

People claim that
HasOne / one-to-one is usually reserved for a special case. Generally, you'd use a References / many-to-one relationship in most situations (see: I think you mean a many-to-one). If you really do want a one-to-one, then you can use the HasOne method.
If you really do want a one-to-one and use it, you should remember that entities are joined by their ids by default.
If you check generated SQL you'll see something like JOIN Location ON Location.Id = TimeRecord.Id.
In order to get SQL like JOIN Location ON Location.TimeRecordId = TimeRecord.Id you should specify the foreign key via PropertyRef() method. So your mapping could be the folloving:
public class TimeRecordMap : ClassMap<TimeRecord>
{
public TimeRecordMap()
{
Id(x => x.Id);
Map(x => x.Description);
Map(x => x.StartTime);
Map(x => x.EndTime);
HasOne(x => x.Location).Cascade.All().PropertyRef(it => it.TimeRecord);
}
}
public class LocationMap : ClassMap<Location>
{
public LocationMap()
{
Id(x => x.Id);
Map(x => x.Longitude);
Map(x => x.Latitude);
Map(x => x.Adress);
References(x => x.TimeRecord/*, "TimeRecordId"*/).Unique().Not.Nullable();
}
}
In order to make sure that any location has TimeRecord you can add .Not.Nullable() into your LocationMap class.