Cannot add FK using EntityFramework

Question

I'm learning ASP.NET Core with Entity Framework and I'm trying to add an FK in my UserDetails table. These are the model:

public class User
{
    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }

    public virtual UserDetails UserDetail { get; set; }
}

public class UserDetails
{
    public string UserId { get; set; }
    public string Biography { get; set; }
    public string Country { get; set; }
    public Uri FacebookLink { get; set; }
    public Uri TwitterLink { get; set; }
    public Uri SkypeLink { get; set; }

    public virtual User UserKey { get; set; }
}

The table User is the Master table which contains all the registered user in my application (I'm using AspNetCore.Identity).

Actual I want add as FK the property UserId which must bound the Id of User . So inside the ApplicationContext class I did the following:

public class DemoAppContext : IdentityDbContext<ApplicationUser>
{
   public DemoAppContext(DbContextOptions<DemoAppContext> options) : base(options)
   {
   }

   protected override void OnModelCreating(ModelBuilder builder)
   {
       builder.Entity<UserDetails>(entity =>
       {
           entity.Property(e => e.Biography).HasMaxLength(150);

           entity.Property(e => e.Country).HasMaxLength(10);

           entity.HasOne(d => d.UserKey)
                 .WithOne(p => p.UserDetail)
                 .HasForeignKey(d => d.???; <- problem here
       });
   }

   public DbSet<User> Users { get; set; }
   public DbSet<UserDetails> UserDetails { get; set; }
}

I overrided the OnModelCreating and using the ModelBuilder I defined for UserDetails table the MaxLength of some properties. In the last line of builder.Entity<UserDetails> I tried to assign the FK creating the relationship with HasOne => UserKey which contains the object User . The relationship is 1 to 1 so I used WithOne and assigned UserDetail which contains the UserDetails object.

At the end I used HasForeignKey but when I type d. the compiler doesn't show any properties.

What I did wrong? Maybe I overcomplicated the things?

Sorry for any errors, and thanks in advance for any explanation.

Answer 1

The following code will work:

builder.Entity<UserDetails>(entity =>
{
    entity.Property(e => e.Biography).HasMaxLength(150);
    entity.Property(e => e.Country).HasMaxLength(10);

    entity.HasOne(d => d.UserKey)
              .WithOne(p => p.UserDetail)
          .HasForeignKey<UserDetails>(x => x.UserId);  //???; < -problem here
});

Answer 2

Can you try this:

        entity.HasOne(d => d.UserKey)
                      .WithOne(p => p.UserDetail)
                      .HasForeignKey<User>(b => b.Id);

or

public class UserDetails
{
    [ForeignKey(nameof(UserKey))]
    public string UserId { get; set; }
    public string Biography { get; set; }
    public string Country { get; set; }
    public Uri FacebookLink { get; set; }
    public Uri TwitterLink { get; set; }
    public Uri SkypeLink { get; set; }

    public virtual User UserKey { get; set; }
}