NHibernate - Query with value object containing NULL values - nhibernate

Question

I have a value object like this:
public class PersonMapping : ComponentMap<Person>
{
public PersonMapping()
{
Map(x => x.FirstName).Not.Nullable().Length(96);
Map(x => x.LastName).Not.Nullable().Length(96);
Map(x => x.MiddleName).Nullable().Length(96);
Map(x => x.NickName).Nullable().Length(64);
}
}
I create a query like so:
var owner = new Person("Anneliese", "ObjectOfficer_1");
var query = NhSession.Query<ServiceContract>()
.Where(s => s.ObjectOfficer.Manager == owner);
contracts = query.ToList();
This creates an instance of Person that has a null MiddleName and Nickname. NHibernate creates a query like so:
select .....
from .....
where (objectoffi1_.FirstName = #p0
and objectoffi1_.LastName = #p1
and objectoffi1_.MiddleName = #p2
and objectoffi1_.NickName = #p3);
#p0 = 'Anneliese' [Type: String (4000)],
#p1 = 'ObjectOfficer_1' [Type: String (4000)],
#p2 = NULL [Type: String (4000)],
#p3 = NULL [Type: String (4000)]
No records match which is wrong.
When I change the generated query and replace the parameters with values like so:
...
where (objectoffi1_.FirstName = 'Anneliese' and objectoffi1_.LastName = 'ObjectOfficer_1'
and objectoffi1_.NickName is null and objectoffi1_.MiddleName is null)
it returns a correct number of results. Does anybody know how to deal with this? If NHibernate sends field = NULL instead field is null to MS SQL Server, no results are returned since it is wrong TSQL. Any ideas?

Answer 1

Turns out, that it is not possible to put value objects with nullable properties in a where clause. You have to care about these potential null values yourself in your code. Once you compare the fields directly field by field it works. Here the 'correct' version:
var query = NhSession.Query<ServiceContract>()
.Where(s => s.ObjectOfficer.Manager.FirstName == owner.FirstName
&& s.ObjectOfficer.Manager.LastName == owner.LastName);
contracts = query.ToList();
I think this is more than just inconvenient and I do not know if other ORMs such as EF have the same problem. Value Objects are an important building block of DDD.