Entity Framework 6.1.3 Mapping Foreign key to non primary key

Question

The goal is to have an API with all the fields from the GravityZone with the name of the zone coming from the Zone table. I've tried several permutations of the following code without success. It's currently coming up with null for the Zone which I'm hoping to get either the name as a string or part of the object. I'm working with existing tables that I'm not able to modify.

Models:

public partial class Zone
{
    [Key]
    [Column("ZONE_ID")]
    public decimal ZoneId { get; set; }

    [Column("ZONE_CODE")]
    public decimal ZoneCode { get; set; }

    [Column("ZONE_NAME")]
    public string ZoneName { get; set; }

    public virtual ICollection<GravityZone> GravityZones { get; set; }
}

public partial class GravityZone
{
    [Key]
    [Column("GRAVITY_ID")]
    public decimal GravityZoneId { get; set; }

    [Column("ZONE_CODE")]
    public decimal ZoneCode { get; set; }

    [Column("ELEVATION")]
    public decimal Elevation { get; set; }

    [Column("REMARK")]
    [StringLength(2000)]
    public string Remark { get; set; }

    public virtual Zone Zone { get; set; }
}

Context (only the relational portion)

modelBuilder.Entity<Zone>()
    .HasKey(e => e.ZoneCode);

modelBuilder.Entity<GravityZone>()
    .HasRequired(e => e.Zones);

Everything else comes back great except for this part:

"Zones":null,

Answer 1

This is now possible in Entity Framework 7 (that is, EF Core 1.0).

From .Net Entity Framework User Voice Unique Constraint (i.e. Candidate Key) Support:

Support for this feature was added in EF Core 1.0 and we don’t have plans to add it in the EF6 codebase.

Answer 2

I don't think it is possible cause it would cause a lot of trouble. Foreign key should should always point to some key of a table. I don't think you are able to tell EF about candidate keys.

Edit:

Similar Questions: Entity Framework 5.0 composite foreign key to non primary key - is it possible?

Here is answer for your question. As I thought EF does not understand the concept of uniqueness with exception of primary key.

Entity Framework foreign keys to non-primary key fields