如何使用数据注释在实体框架中设置外键？

Question

I am trying to build a web application that connects to a SQL Server using Entity Framework. I have three classes, one is to register consultations, the second one is for registering contact information and the last one is to classify consultations types (kind of like an enumerable but I need to store more data).

Every consultation has a contact information (so there is a reference to the primary key of table Contact ) and a ConsultationType (another reference to the primary key of table Type ).

public class Consultation
{
    [Key]
    public long id { get; set; }

    public long ContactID { get; set; }
    [ForeignKey("ContactID")]
    public Contact Contact { get; set; }

    public long ConsultationTypeID{ get; set; }
    [ForeignKey("ConsultationTypeID")]
    public ConsultationType Type { get; set; }
}

public class Contact
{
    public long id { get; set; }
    public string Name { get; set; }
    public string Email { get; set; }
}

public class ConsultationType
{
    public long id { get; set; }
    public string type{ get; set; }
    public string abbreviated{ get; set; }
} 

The Consultation table has 3 columns ( id , ContactID and ConsultationTypeID ). I am expecting all the Contact and ConsultationType references to be filled automatically based on the ID in the foreign keys.

Currently when I retrieve data from the database, only the ConsultationType gets filled, not the contact. I can not understand this behaviour because I think I have all set up the same way.

EDIT : when I retrieve Consultation data, I get a list of objects with 5 properties (consultation ID, contact ID, contact, consultation type Id, consultation type). 4 of them are set (only contact is not set). I want the contact property to be set to an instance of the row that contains the ID referenced by the Contact ID property.

Answer 1

Rereading the select part.

consultationTypes = await _context.ConsultationTypes.ToListAsync();
Consultation = await _context.Consultations.ToListAsync();

I thought that maybe I should load the Contact also. So I have added:

await _context.ConsultationTypes.ToListAsync();
await _context.Contacts.ToListAsync();
Consultation = await _context.Consultations.ToListAsync();

I don't really understand why I need to do it, but it is working now. I wonder if there is a way to load all tables so I don't have to do it every time.