NHibernate / ActiveRecord: How to set foreign key without getting entire object?

Question

Let's say I've got the following ActiveRecord class:

[ActiveRecord]
public class Account
{
    ...

    [BelongsTo("CustomerId")]
    public Customer Customer { get; set; }
}

Currently, to set the value of the CustomerId field I have to get the entire Customer object from the database and assign it to the Account:

Customer customer = Customer.FindById(1);
account.Customer = customer;

This isn't very efficient. I'd rather set the value of CustomerId field directly without round-tripping the database, e.g.

account.CustomerId = 1;

What's the correct way to do this?

Answer 1

You can implement MK8k's solution in ActiveRecord. It would look like this:

using (new SessionScope()) {
    var ghostCustomer = Customer.Find(customerId);

    var account = Account.TryFind(accountId);
    account.Customer = ghostCustomer;
}

Two important points:

The Customer.Find must be in a SessionScope. The Find method checks and will fully load your object if a SessionScope is not defined.

The Customer class must be defined as lazy. NHibernate will not use a proxy for a non-lazy class.