NHibernate - possible to fetch a collection after querying? - nhibernate

Question

There's sooo much literature about fetching and eager loading when doing the actual query using .Fetch
But, once I have a loaded entity - with an empty collection (because I chose not to eager load at query time due to the cartesian product side-effect), can I choose to load a collection a bit later on, say after I've done some paging and I have a concrete List of items?
something like:
var list = (some linq over Session.Query<Entity>)
.Take(10).Skip(2)
.Fetch(x => x.MyCollection)
.ToList();
Session.Fetch<Entity>(list, l => l.OtherCollection);
Edit
The point is - i'm already fetching 2 child collections in the Query - makes the query and result set quite sizeable already (see nhibernate Cartesian product). I'd like page the results, get a list of 10 then optionally go back to the database to populate child collection properties of the paged (10, say) result. This is a performance consideration.

Answer 1

Issue this query
/*we dont need the result*/Session.QueryOver<Entity>()
.Where(x => x.Id.IsIn(list.Select(l => l.Id)))
.Fetch(l => l.OtherCollection)
.ToList();
then nhibernate should initialize the collections on the Entities
EDIT:
to improve initial loading time see http://ayende.com/blog/4367/eagerly-loading-entity-associations-efficiently-with-nhibernate
then you can do for exmaple
var results = (some linq over Session.Query<Entity>)
.Take(10).Skip(2)
.ToList();
var q = Session.QueryOver<Entity>()
.Where(x => x.Id.IsIn(list.Select(l => l.Id)))
.Fetch(l => l.MyCollection)
.ToFuture();
Session.QueryOver<Entity>()
.Where(x => x.Id.IsIn(list.Select(l => l.Id)))
.Fetch(l => l.OtherCollection)
.ToFuture();
Session.QueryOver<Entity>()
.Where(x => x.Id.IsIn(list.Select(l => l.Id)))
.Fetch(l => l.ThirdCollection)
.ToFuture();
return q.ToList()

Answer 2

I've just gone off to read about futures and projections in NHibernate which look promising as a solution...will post more when I find out about it.
This is a solution: http://ayende.com/blog/4367/eagerly-loading-entity-associations-efficiently-with-nhibernate, but I still do not like it, as my query itself is quite expensive (uses '%like%# + paging), so executing 3 or 4 times just to load collections seems expensive
Edit
This is what I have. Lookign at the sql generated, the correct sql is being run and returning expected results, but the collections on the returned results are null. Can you see what's missing?:
public List<Company> CompaniesForLoggedInUser(int pageSize, int pageNumber)
{
var list =
QueryForCompaniesFor(SecurityHelper.LoggedInUsername)
.Page(pageNumber, pageSize)
.ToList()
.FetchCompanyCollections(Session);
return list;
}
internal static class CompanyListExtensions
{
internal static List<Company> FetchCompanyCollections(this List<Company> companies, ISession session)
{
var ids = companies.Select(l => l.Id).ToArray();
session.QueryOver<Company>()
.Where(x => x.Id.IsIn(ids))
.Fetch(l => l.Properties).Eager()
.Future();
return session.QueryOver<Company>()
.Where(x => x.Id.IsIn(ids))
.Fetch(l => l.UserAccessList).Eager()
.Future()
.ToList();
}
}