ISession.Load returns object with zero ID

Recently we had a following problem with NHibernate, and although I love NHiberante, it does not always behave as expected.

We have a Person class correctly mapped in NHibernate:

public class Person
{
	public int Id { get; set; }
	public int Name { get; set; }
}

We saw that sometimes we were getting a Person with Id equal to zero, from our repository:

public class PersonRepository
{
	private ISession _session;

	//...

	public Person LoadById(int id)
	{
		return _session.Load<person>(id);
	}
}

We narrowed the problem down and wrote this little test:

[Test]
public void LoadById_Loads_IdIsSet()
{
    _context.ExecuteInTransaction(() =>
		{
			Person person = _context.PersonRepository.LoadById(7);
			Assert.AreEqual(7, person.Id);
		}
	);
}

…which of course failed.

After initial surprise, we took a second look at the Person class and we saw that we are missing virtual keyword on properties. NHibernate is not able to create a correct Proxy object.

public class Person
{
	public virtual int Id { get; set; }
	public virtual int Name { get; set; }
}

This fixed the issue.
Strange thing is that we expect that NHibernate would throw an exception is such case.

Tags: NHibernate