I am using NHibernate on a .Net 2.0 project.

I have my mappings working fine and the data is persisting to the database. But, I want to use lazy loading. (At least, I *think* I do.) However, I cannot get it to work. When I load an object, all of the collections come with it. There is a deep chain of objects, (User > UserDetail > Role > RoleDetail > Permission > PermissionDetail) so I don't want to always load all of that data.

I have two guesses as to the problem.

My first guess is, because I'm using generics, whatever it is that makes lazy loading work fails because NHibernate doesn't understand generics.

My second guess is, if the generics aren't a problem, there is something wrong with the way I'm mapping my collections.

I'll wait to hear an answer for guess #1 before getting into my mapping details.

--Brian

I had a similar problem earlier on and the reason turned out to be that I had not defined the properties of the class that was to be lazily loaded as virtual.
Please check that the class that are meant to be lazily loaded are marked lazy=true in the mapping document and that all the properties are marked virtual.

Okay, I had to fix my class by added "lazy = true" to my child class's mapping.

So now my child class is marked lazy, my parent class's collection is marked lazy and all of the child class' properties are virtual.

But, it still doesn't work.

When I load a User, I still get the UserDetails collection populated and the rest of the objects below that.

I'm loading a User like this:



Is this wrong? Do I need to load it a special way to enable lazy loading?

--Brian

Have you tried to use ISession.Get() instead of ISession.Load() in order for lazy loading to work?

Best regards, jorgas

I tried this too, but it still loads everything.

The log from using Load() looks the same as using Get().

How do you know it's not lazy loading? Are you looking at the SQL or testing to see if the object is loaded after closing the session?

one of the solutions is to use non-generic collection as fields and let Nhibernate directly access them and use generic collection wrappers as properties to expose this field to the rest of your application. In this way you don't need to "guess" how Nhibernate is going to work with generic collections.
Here is an article about a Generic ISet and a set of simple wrappers:
http://www.codeproject.com/csharp/GenericISet.asp