Hi,

I have two classes:
- Person is a baseclass.
- Employee is a subclass of Person.

These two correspond with the following database tables in a MSSQL database:
- tblPerson. The primary key is personid, an identity field.
- tblEmployee. The primary key is personid.

When I make a new employee, the following happen:
- A new record in tblPerson is made. The identity primary key generates a new number for the primary key.
- A new record in tblEmployee is made (with the corresponding primary key in tblPerson).

OK now I would like to use an existing Person and associate it to a new employee.

Person person = new Person("MyName")
session.SaveOrUpdate(person)
...
...later
...
Employee employee = new Employee()
...then I don't know, employee.Id must be equal to person.Id.

Is it possible ?

Greets,
Gicks

Generally, yes, ID of your Employee must be the same as the ID of the Person you are extending.

There is a problem, though: from the database prospective your object will be partially new and partially existing. Its "person" part already exists, while its "employee" part doesn't. I afraid in this case neither ISession.Save, nor ISession.Update could work correctly. Perhaps you will need to create record in tblEmployee table by hands and then Update the object.

If a Person can move to an employee, you may think about using roles instead of inheritance...

Anyway, in your case, you can copy all the information from the person the employee and save it (as long as you don't care about not having the original person.Id)