Define Entity Framework relationships using foreign keys only by FluentAPI

Question

Is any way of defining Entity Framework relations using foreign keys only (no virtual properties of reference type) with FluentAPI (data models should not be changed)?

CardDataModel

public class CardDataModel
{
    public int CardId { get; set; }

}

CheckItemDataModel

public class CheckItemDataModel
{
    public int CheckItemId { get; set; }
    public int CardId { get; set; }
}

I'm not sure I understand your question. A navigation property *is* a virtual property of reference type. — Akos Nagy, Sep 01 '17 at 11:39
Akos Nagy, no. A navigation property is CardId in CheckItemDataModel. Models shouldn't be changed. Definition should be done by FluentAPI only — Alex Zaitsev, Sep 01 '17 at 11:42
CardId is called a *foreign key property*. A navigation property is by definition a property that holds a reference to the other of the association. Here's a more detailed description: https://learn.microsoft.com/en-us/dotnet/framework/data/adonet/navigation-property — Akos Nagy, Sep 01 '17 at 11:52
Can I ask why do you want this? What are the advantages of having a model class/object without Navigation properties? — AndrasCsanyi, Sep 01 '17 at 12:09
You cannot define a relationship without a navigation property. The navigation property *is* the relationship. If you only have the foreign key property, then you always have to explicit query for the related objet yourself, you have no relationship fixup (because you don't have a realtionship) etc. The only thing you can do is map the foreign key property to an actual foreign key in the database with migrations, but you can set that up manually as well in the db, without affecting the model. — Akos Nagy, Sep 01 '17 at 12:15

score 9 · Accepted Answer · answered Sep 01 '17 at 13:47

Yes, it's possible in EF Core. It wasn't in EF6 and below, but now EF Core provides parameterless overloads of HasMany / HasOne which allow configuring such relationship:

modelBuilder.Entity<CardDataModel>()
    .HasMany<CheckItemDataModel>() // <-- note this
    .WithOne()
    .HasForeignKey(e => e.CardId);

score -2 · Answer 2 · answered Sep 01 '17 at 11:27

-2

You could do this.

public class Card
{
    public int Id { get; set; }
}

public class CheckItem
{
    public int Id { get; set; }
    public int CardId { get; set; }
    public virtual Card Card { get; set; }
}

answered Sep 01 '17 at 11:27

Maritim

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It seems you missed the part where OP wrote *no virtual properties of reference type* – DavidG Sep 01 '17 at 11:32
Thanks for your response, but models shouldn't be changed and definition should be done by Fluent API – Alex Zaitsev Sep 01 '17 at 11:40
Whoops.. sorry :) – Maritim Sep 01 '17 at 11:45
May I ask why you don't want them to be virtual @AlexZaitsev? – Maritim Sep 01 '17 at 11:46
@Maritim, I don't want data models to know about Entity Framework. Your way is Entity Framework style – Alex Zaitsev Sep 01 '17 at 12:03
3

@AlexZaitsev The fact that the property is virtual is not equal to informing the models about the existence of EF. If you were using annotations then I'd agree with you. – Maritim Sep 01 '17 at 12:16

Define Entity Framework relationships using foreign keys only by FluentAPI

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