FirstOrDefault returns null on foreign key

Question

Lets say we have the following model :

public class ReadingOrder
{
    public virtual int Id { get; set; }
    public virtual Order Order { get; set; }
}

Mapping:

Table("db_ReadingOrder");
Id(o => o.Id).Column("Id").GeneratedBy.Identity();
References(o => o.Order, "OrderId");

I want to get the ReadingOrder which has the orderId equal with 1 (eg). But when I try a FirstOrDefault, the query returns null :

var readingO = _repositoryFactory.GetRepository<ReadingOrder>().FirstOrDefault(xz => xz.Order.Id == 1);

If I get all of them and after apply a FirstOrDefault works, but its stupid:

var readingOrderList1 = _repositoryFactory.GetRepository<ReadingOrder>()
                         .GetAll().FirstOrDefault(xz => xz.Order.Id == 1);

The method from repository has the following format:

public T FirstOrDefault(Expression<Func<T, bool>> predicate)
{
   return _session.Query<T>().FirstOrDefault(predicate);
}

easy stuff, but not working. If I go for a normal property, like Id, all works as expected. Also, if I get the generated query from log and put it in sqlite, it runs successfully and the reading order is returned. Is there a bug in NHibernate? Is a mapping problem? Or is it a problem with SQLite?

Answer 1

Ok, finally I found the problem : the name of the foreign key column "OrderId". Nhibernate looks for "Hibernate.Order" in this case, I don`d know why, but after I changed the name of the column, the item is now retrieved from db. Thank you all for your answers! I gave the bounty to user Syed Farjad Zia Zaidi, because he helped me to isolate the problem. It was clear that was an Nhibernate issue, so thank you again.