Foreign key with Entity Framework

Question

I have two model classes User and Reclamation, the Reclamation class have a foreign key for a User object, here are my two classes :

public class User
{
    [Key, ScaffoldColumn(false), Display(Name = "ID User")]
    public int idUser { set; get; }

    [Required, StringLength(16), Display(Name = "Login")]
    public string login { set; get; }

    [Required, StringLength(16), Display(Name = "Password")]
    public string password { set; get; }
}

public class Reclamation
{
    [Key, ScaffoldColumn(false), Display(Name = "ID Reclamation")]
    public int idReclamation { set; get; }

    [ForeignKey("idUser")]
    public User user{ set; get; }

    [Required, Display(Name = "ID Rapporteur")]
    public int idUser { set; get; }

    [Required, StringLength(30), Display(Name = "Message")]
    public string message{ set; get; }
}

Lets say for example that i have a user with an idUser=1. When i create a new Reclamation with idUser=1 it will be inserted fine in the database but my problem with the User object it doesn't contains the informations of the user with the idUser=1, should i code that manually in the set Property of the idUser attribute on the Reclamation class or i'm missing something ?

Can you just retrieve the user object from the database and then attach a reclamation to it? Rather than manually add the user ID to the new reclamation? You will find it is better to work with the entity graph in EF than trying to do things manually. — lintmouse, Mar 17 '15 at 22:28
I think i can do it but i'm asking if there is an automatic way to do that instead of adding it manually. — user3578325, Mar 17 '15 at 22:37

score 2 · Answer 1 · answered Mar 18 '15 at 04:15

2

you should try this code:

UserData.Include("Reclamation").ToList();

answered Mar 18 '15 at 04:15

user3567028

41
2

score 2 · Accepted Answer · answered Mar 18 '15 at 07:06

You can add a virtual property to your entity class to enable Lazy Loading. This way you you will enable EF to load the related object when it is requested.

        public class User
        {
            [Key, ScaffoldColumn(false), Display(Name = "ID User")]
            public int idUser { set; get; }

            [Required, StringLength(16), Display(Name = "Login")]
            public string login { set; get; }

            [Required, StringLength(16), Display(Name = "Password")]
            public string password { set; get; }

            public virtual Reclamation Reclamation {get; set;}

            /*if you have one to many relationship, use Collection<T> 
   and initialize it in the constructor Reclamations = new Collection<Reclamation>();*/
            public virtual Collection<Reclamation> Reclamations {get; set;}
        }

Your other option is to use Eager Loading, as mentioned above. Something like:

context.Users.Include(x => x.Reclamations).ToList();

it worked fine thanks, but can you explain for me why it didn't worked without the virtual property ? what is the role of virtual here ? — user3578325, Mar 18 '15 at 12:35
It`s a rule/convention/ in Entity Framework, which enables Lazy Loading. The answer here http://stackoverflow.com/questions/7738722/entity-framework-4-1-virtual-properties has detailed explanation. — vortex, Mar 18 '15 at 12:44

Foreign key with Entity Framework

2 Answers2