Short Answer
No, it is not possible to "upgrade" an already persisted object to its subclass. Nhibernate simply doesn't support this. That's why you see 2 customers and one member entry. This is actually the expected behavior because Nhibernate simply creates a copy with a new ID of the object instead of creating the reference to Member...
So basically you could do either
- Copy the data of Customer into Member, delete customer and save Member
- Use a different object structure without subclasses where Member is a different table with it's own ID and a reference to Customer
- Use native sql to insert the row into Member...
Some example:
Your classes could look like this
public class Customer
{
public virtual Guid Id { get; set; }
public virtual string Name { get; set; }
}
public class Member : Customer
{
public virtual string MemberSpecificProperty { get; set; }
}
Basically, Member could have additional properties, but will have the same properties as Customer of cause, too.
public class CustomerMap : ClassMap<Customer>
{
public CustomerMap()
{
Id(x => x.Id)
.GeneratedBy.GuidComb();
Map(x => x.Name);
}
}
and for the sub class, you have to map additional properties only!
public class MemberMap : SubclassMap<Member>
{
public MemberMap()
{
Map(x => x.MemberSpecificProperty);
}
}
testing it
{
session.Save(new Customer()
{
Name ="Customer A"
});
session.Save(new Member()
{
Name = "Customer B",
MemberSpecificProperty = "something else"
});
session.Flush();
}
This will create 2 entries in the customer table and one row into Member table. So this is as expected, because we created one customer and one member...
Now the "upgrade" from Customer A to Member:
using (var session = NHibernateSessionFactory.Current.OpenSession())
{
session.Save(new Customer()
{
Name ="Customer A"
});
session.Flush();
}
using (var session = NHibernateSessionFactory.Current.OpenSession())
{
var customer = session.Query<Customer>().FirstOrDefault();
//var member = customer as Member;
var member = new Member()
{
Name = customer.Name,
MemberSpecificProperty = "something else"
};
session.Delete(customer);
session.Save(member);
session.Flush();
}