Include several references on the second level

问题

Assume we have this model :

public class Tiers
{
    public List<Contact> Contacts { get; set; }
}

and

public class Contact
{
    public int Id { get; set; }
    public Tiers Tiers { get; set; }
    public Titre Titre { get; set; }
    public TypeContact TypeContact { get; set; }
    public Langue Langue { get; set; }
    public Fonction Fonction { get; set; }
    public Service Service { get; set; }
    public StatutMail StatutMail { get; set; }
}

With EF7 I would like to retrieve all data from the Tiers table, with data from the Contact table, from the Titre table, from the TypeContact table and so on ... with one single instruction. With Include/ThenInclude API I can write something like this :

_dbSet
     .Include(tiers => tiers.Contacts)
          .ThenInclude(contact => contact.Titre)
     .ToList();

But after Titre property, I can't include others references like TypeContact, Langue, Fonction ... Include method suggests a Tiers objects, and ThenInclude suggests a Titre object, but not a Contact object. How can I include all references from my list of Contact? Can we achieve this with one single instruction?

回答1:

.ThenInclude() will chain off of either the last .ThenInclude() or the last .Include() (whichever is more recent) to pull in multiple levels. To include multiple siblings at the same level, just use another .Include() chain. Formatting the code right can drastically improve readability.

_dbSet
    .Include(tiers => tiers.Contacts).ThenInclude(contact => contact.Titre)
    .Include(tiers => tiers.Contacts).ThenInclude(contact => contact.TypeContact)
    .Include(tiers => tiers.Contacts).ThenInclude(contact => contact.Langue);
    // etc.

回答2:

For completeness' sake:

It is also possible to include nested properties directly via Include in case they are not collection properties like so:

_dbSet
    .Include(tier => tier.Contact.Titre)
    .Include(tier => tier.Contact.TypeContact)
    .Include(tier => tier.Contact.Langue);

来源：https://stackoverflow.com/questions/30072360/include-several-references-on-the-second-level