Eagerly fetch multiple collection properties (using QueryOver/Linq)?

Question

I found 2 similar questions:

• Multiple Fetches in linq to nhibernate
• Is this the right way of using ThenFetch() to load multiple collections?

Answer 1

I prefer to use the linq provider if at all possible especially if you are using newer versions of nhibernate (>= 4.0). As long as you have your collections mapped as ISets (requires .net framework >= 4) which we converted to such that we could do eager loading and avoid cartesian products. I feel like this isn't something that is heavily advertised but I prefer this method where applicable over anything else :

public class Person
{
    public virtual int Id { get; private set; }
    public virtual ISet Books { get; set; }
    public virtual ISet
 Articles { get; set; }
    public virtual ISet
 Addresses { get; set; }
}

public Person()
{
    this.Books = new HashSet();
    this.Articles = new HashSet
();
    this.Addresses = new HashSet
();
}

If you have your collections defined like the above then you can do the following and still avoid cartesian product issues:

var persons = session.Query()
                     .FetchMany(x => x.Books)
                     .FetchMany(x => x.Articles)
                     .FetchMany(x => x.Addresses)
                     .ToList();