Initialize associated entity or collection fails with Stateless Session in NHibernate

Question

I'm trying to make an association with an entity from 3rd party dll. For some reasons, I have to use StatelessSession. With StatefullSession it works but not with Stateless. The idea is to allow 3rd party to add a table and have its data fetched when I query the main table.

I have three projects: my main project, model project with the IExtender interface, and 3rd party project with Extender class (not referenced by the main project).

My data schema:

Table Data
   Id INT identity,
   more fields...

Table Extender
   Id INT PK, FK from Data
   Name NVARCHAR
   more fields...

Model project code:

public interface IExtender
{
    int Id { get; set; }
}

Main project code:

public class Data
{
    public virtual int Id { get; set; }
    public IExtender Extender { get; set; }
    //public IList<IExtender> Extenders { get; set; }
}

Main project hbm:

<?xml version="1.0" encoding="utf-8"?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
  namespace="..." assembly="..." auto-import="true">

<class name="Data" table="Data" lazy="false">
    <id name="Id" column="Id" type="int" >
      <generator class="identity" />
    </id>
    <one-to-one name="Extender" foreign-key="Id" 
           class="Model.IExtender, Model" lazy="false"/>

<!--<bag name="Extenders" cascade="all" inverse="true" lazy="false">
  <key column="Id" />
  <one-to-many class="Model.IExtender, Model"/>
</bag>-->

</class>
</hibernate-mapping>

3rd party project:

public class Extender : IExtender
{
    public virtual int Id { get; set; }
    public string Name { get; set; }
}

3rd party hbm:

<?xml version="1.0" encoding="utf-8"?>

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" namespace="Model" assembly="Model" auto-import="true">

  <class name="IExtender" table="IExtender" lazy="false" abstract="true">

    <id name="Id" column="Id" type="int" >
      <generator class="assigned" />
    </id>

    <union-subclass table="Extender" name="Extension.Extender, Extension" lazy="false">
      <property name="Name" column="Name" not-null="true" type="String" />
    </union-subclass>

  </class>
</hibernate-mapping>

3rd party project puts its dll in the main project bin folder.

Now my code to get the data looks like:

var sessionFactory = new Configuration().Configure()
   .AddAssembly(Assembly.LoadFile(System.Environment.CurrentDirectory + @"\Extender.dll"))
   .AddAssembly(Assembly.GetExecutingAssembly())
   .BuildSessionFactory();

var session = sessionFactory.OpenStatelessSession();
var criteria = session.CreateCriteria<Data>();
var data = criteria.List<Data>().ToList();
Console.WriteLine(data.First().Extender.Id); // fails because Extender is null

If I use StatefullSession, it is working fine with a single entity or a bag. If I use StatelessSession and a bag instead (and a list as the commented rows above), I get an error:

collections cannot be fetched by a stateless session

If I remove the lazy="false" from the bag, I get this error (no matter if the collection is virtual or not):

Initializing[MyProject.Data#1]-failed to lazily initialize a collection of role: MyProject.Data.Extenders, no session or session was closed

EDIT: I upgraded my NHibernate version to the latest and now it is working when I use a bag, but when I use a single entity with one-to-one relation it is always null.

By the way, no matter if there is an error or not, I see in the final sql query that Extender table is being joined properly.

Thanks for your help.

Initialize associated entity or collection fails with Stateless Session in NHibernate

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