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

public IList<Person> GetAll()
{
    var persons = session.QueryOver<Person>()
        .Future<Person>();

    session.QueryOver<Person>()
        .Fetch(x => x.Books).Eager
        .Future<Person>();

    session.QueryOver<Person>()
        .Fetch(x => x.Articles).Eager
        .Future<Person>();

    session.QueryOver<Person>()
        .Fetch(x => x.Addresses).Eager
        .Future<Person>();

    return persons.ToList();
}

Answer 2

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<Book> Books { get; set; }
    public virtual ISet<Article> Articles { get; set; }
    public virtual ISet<Address> Addresses { get; set; }
}

public Person()
{
    this.Books = new HashSet<Book>();
    this.Articles = new HashSet<Article>();
    this.Addresses = new HashSet<Address>();
}

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<Person>()
                     .FetchMany(x => x.Books)
                     .FetchMany(x => x.Articles)
                     .FetchMany(x => x.Addresses)
                     .ToList();