Foreign Key To Microsoft.AspNet.Identity.EntityFramework.IdentityUser?

Question

I'm in VS 2013 and have just created an MVC application.

I'm creating an object I intend to have a foreign key to the AspNetUsers table in the resulting database. The project does have an ApplicationUser (deriving from IdentityUser) that looks like a property-column match with the AspNetUsers table.

How do we properly declare a foreign key to this?

public MyObject
{
   public string UserId { get; set; }

   [ForeignKey("UserId")]
   public ApplicationUser User { get; set;}

   // other properties
}

Now, I modify ApplicationUser to have a collection of MyObjects:

public ApplicationUser : IdentityUser
{
     public virtual ICollection<MyObject> MyObjects { get; set; }    
}

This seems to be how to do one-to-many in EF Code First. However, when I update-database, I'm getting the errors that say Identity members (IdentityUserLogin, IdentityUserRole, etc.) have no keys defined. Perhaps those classes were not meant to participate in EF Code First Migrations?

I could go "to the back" and add the foreign key via SQL statements, but if I wanted to update again from Code First, I might get errors (that the database doesn't currently match the older migration or something like that).

How do we properly foreign-key reference those membership tables?

I also tried to create an AspNetUser class with matching properties of the AspNetUsers table. Instead of "public ApplicationUser" on the Client class, I declared "public AspNetUser". Doing this resulted in a migration failure - "Automatic migration was not applied because it would result in data loss."

So, what to do?

Answer 1

It is easy to create a one-to-many relationship between ApplicationUser and MyObject and add a "UserId" foreign key in your MyObjects table. What I like about this solution is that it follows EF conventions and there is no need for [ForeignKey] attribute in your model:

public class ApplicationUser : IdentityUser
{
    public virtual ICollection<MyObject> MyObjects { get; set; }
}

public class MyObject
{
    public int MyObjectId { get; set; }

    public string MyObjectName { get; set; }

    // other properties

    public virtual ApplicationUser ApplicationUser { get; set; }
}

public class ApplicationDbContext : IdentityDbContext<ApplicationUser>
{
    public ApplicationDbContext()
        : base("DefaultConnection", throwIfV1Schema: false)
    {
    }

    public DbSet<MyObject> MyObjects { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);

        modelBuilder.Entity<MyObject>()
            .HasRequired(c => c.ApplicationUser)
            .WithMany(t => t.MyObjects)
            .Map(m => m.MapKey("UserId"));
    }
}

Notice the use of Fluent API to create a "UserId" foreign key in your MyObjects table. This solution would still work without adding the Fluent API, but then your foreign key column would be named "ApplicationUser_Id" in your MyObjects table by convention.