Why is my IList <T> returned as a list of null objects?

Question

As long as I understand that Set or Bag is probably the right way to do this, I'm new to NHibernate and I'm trying to figure out why the following happens.

I have two classes:

public class Customer
{
  public virtual int Id { get; protected set; }
  public virtual string CustomerName { get; set; }
  // Customer has many domains
  public virtual IList<Domain> Domains { get; set; }
}

public class Domain
{
  public virtual int Id { get; protected set; }
  public virtual int CustomerID { get; set; }
  public virtual string DomainName { get; set; }
}

My mapping files are as follows:

<!-- Domain -> tblDomains           -->           
<class name="Domain" table="tblDomains">

  <id name="Id">
    <column name="DomainID" sql-type="int" not-null="true"/>
    <generator class="identity"/>
  </id>

  <property name="CustomerID"/>
  <property name="DomainName"/>

</class>

<!-- Customer -> tblCustomer       -->
<class name="Customer" table="tblCustomer">

  <id name="Id">
    <column name="CustomerID" sql-type="int" not-null="true"/>
    <generator class="identity"/>
  </id>

  <property name="CustomerName" column="Customer"/>

  <list name="Domains">
    <key column="CustomerID"/>
    <index column="DomainID"/>
    <one-to-many class="Domain" />
  </list>

</class>

When I return the object Customer, the property Domainscontains a list of 665383 null objects Domain. Element 665384'th in the list contains a valid population.

Only 63 Domainbelong to this client, so I assume that this is some kind of Cartesian product result. I looked into SQL at NHProfiler, but all I see is a query that looks pretty innocent when I iterate over the first item in a list Domains:

SELECT domains0_.CustomerID  as CustomerID1_,
       domains0_.DomainID    as DomainID1_,
       domains0_.DomainID    as DomainID2_0_,
       domains0_.CustomerID  as CustomerID2_0_,
       domains0_.DomainName  as DomainName2_0_
FROM   tblDomains domains0_
WHERE  domains0_.CustomerID = 5667 /* @p0 */

<bag>, . - , ?

Answer 1

. , 63 , 0 62, Domain .

DomainId, , . , 665384 ( , DomainId 1 ), , 63 . ?: -)