流利的NHibernate子类与外键的映射

Question

I have the this objects:

class Person { Int32 id; String name; /*..*/ Adress adress; }
class Employee : Person { String e_g_Tax; /*..*/ Guid relationshipToManagmentId; }

And the follow premises for mapping:
(a) The "relationshipToManagmentId" should be a foreign key.
(b) The table "RelationshipToManagment" is a non-mapped table, (a old part of application)
(c) The mapping strategie is TPT. (at least for new objects :-)

Mapping, until now:

public class PersonMap : ClassMap<Person> {
  public PersonMap(){
    Id(x => x.id);
    Map (x => x.Nachname).Length(255).Not.Nullable();
    /*..*/
    References(x => x.Adresse).Class(typeof(Adresse)).Not.Nullable();
  }
}
public class EmployeeMap : SubclassMap<Employee>
    {
        public EmployeeMap()
        {
            Map(x => x.e_g_Tax, "enjoytax")
                .Not.Nullable();
            /*..*/
            Join("RelationshipToManagment", xJoin =>
            {
                //xJoin.Table("RelationshipToManagment");
                xJoin.Fetch.Join();
                xJoin.KeyColumn("ID");
                xJoin.Map(x => x.relationshipToManagmentId)
                    .Not.Nullable() ;
            }); // --> exception!!

How can i write this?

Answer 1

Join() can only join on the primary key (property id) to the other table but you need to join on a foreign key column. A normal Reference does what you want

class Employee : Person
{
    Management Management;
}

public EmployeeMap()
{
    References(x => x.Management).Column("relationshipToManagmentId");
}

Update: if you need readonly information from the RelationshipToManagment table you could use a formula property

public EmployeeMap()
{
    Map(x => x.RelationshipToManagment).Formula("(SELECT m.Title FROM RelationshipToManagment m WHERE m.Id = relationshipToManagmentId)");
}