Composite primary keys and foreign keys Code First

Question

I'm trying to create 2 entities, user and user reviews, where user reviews has a composite primary keys which are the ids of the users, the one who got reviewed and who did it, this composite primary key is also a foreign key to the primary key in the User's table, however EF is creating an extra column that I don't see the point in it, also when I save to the db an User Review object this column doesn't get populated , it's always empty.

This is causing that when I try retrieve an user with its reviews the reviews collection is always empty unless the User_SubjectId column contains the id of the user.

My query is like this

 return _context.Users
                .Include(u => u.Reviews)
                .Where(u => u.SubjectId.Equals(subjectId));

The Reviews collection always is empty

User Review entity

using System;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace API.Data.Entities
{
    public class UserReview
    {
        [Key, Column(Order = 0), ForeignKey("Reviewer")]
        public string ReviewerId { get; set; } //The user that wrote the review

        [Key, Column(Order = 1), ForeignKey("ReviewedUser")]
        public string ReviewedUserId { get; set; } //The user who was reviewed

        [Required]
        [Range(1, 5)]
        public int Rating { get; set; }

        [Required]
        public DateTimeOffset DateCreated { get; set; }

        [Required]
        public virtual User Reviewer { get; set; }

        [Required]
        public virtual User ReviewedUser { get; set; }
    }
}

The User entity is like this

public class User
    {
        [Key]
        [Required]
        public string SubjectId { get; set; }

        public User()
        {                
            Reviews = new List<UserReview>();
        }

        public virtual ICollection<UserReview> Reviews { get; set; }    
    }

However when I add the migration another columns gets created in my UserReviews table as shown on this picture, the column is User_SubjectId

I don't know if this is a bug in EF or I did my mapping wrong, in any case any ideas?

Thanks

Answer 1

You have to use the ReverseProperty annotation.

public class UserReview
{
    [Key, Column(Order = 0), ForeignKey("Reviewer")]
    public string ReviewerId { get; set; } //The user that wrote the review

    [Key, Column(Order = 1), ForeignKey("ReviewedUser")]
    public string ReviewedUserId { get; set; } //The user who was reviewed

    [Required]
    [Range(1, 5)]
    public int Rating { get; set; }

    [Required]
    public DateTimeOffset DateCreated { get; set; }

    [Required]
    public virtual User Reviewer { get; set; }

    [Required)]
    public virtual User ReviewedUser { get; set; }
}

public class User
{
    [Key]
    [Required]
    public string SubjectId { get; set; }

    public User()
    {                
        Reviews = new List<UserReview>();
    }

    [InverseProperty("ReviewedUser")] // or Reviewer.
    public virtual ICollection<UserReview> Reviews { get; set; }    
}

In my opinon, that's the kind of thing that are easier to configure when using fluent mapping.