How to handle many to many same table (User) in ASP.Net MVC 5 - Fluent API

Question

I am learning ASP.Net MVC 5 and I am stuck with one basic DB Design. So, I have one User which can refer many person in job Also, many person can apply to get themselves Referred. I have created two roles and all of that is taken care. Now, I have on class called Referral which will keep track of every instance of Referral that needs to be done.

Referral Model:

Public class Referral
{
     [Key]
        public int ReferralId { get; set; }
        public Company Company { get; set; }
        public int CompanyId { get; set; }
        public ApplicationUser User { get; set; }
        public string CandidateId { get; set; } // Application User ID of person asking for referral
        public string ReferrerId { get; set; } // Application user ID of person referring the candidate
}

ApplicationUser Model

  public class ApplicationUser : IdentityUser
    {
        public ICollection<Referral> Referrals { get; set; }
        // rest prop removed for brevity sake
    }

Now, suppose A(Referrer) refers B(Candidate). My Table row will look like below.

ReferralId     CompanyId     CandidateId   ReferrerId

1              1             B             A

So, far so good. But I want to establish FK relationship on Referral table. I am new to Fluent API but I tried like below.

    // one candidate can have many referrals
    dBModelBuilder.Entity<ApplicationUser>()
    .HasMany(u => u.Referrals)
    .WithRequired(u => u.User)
    .HasForeignKey(u => u.CandidateId)
    .WillCascadeOnDelete(false);

    //one referrar can have many referrals
    dBModelBuilder.Entity<ApplicationUser>()
    .HasMany(u => u.Referrals)
    .WithRequired(u => u.User)
    .HasForeignKey(u => u.ReferrerId);

But EF respects only one relationship. Why both the foreign key relationhip is not getting set. If I comment out one then other works, and vice versa. But keeping them together as shown never works.

Expected Behaviour: I expected to have two FK relationship. Once I have that then I can work accordingly. Please guide me here. I am new to all this.

Answer 1

As @SLaks mentioned in the comments, in order to have two relationships, you need two havigation properties (one for each FK).

So in the one side replace Referrals property with something like this:

public class ApplicationUser : IdentityUser
{
    // ...
    public ICollection<Referral> ReferrerOf { get; set; }
    public ICollection<Referral> CandidateOf { get; set; }
}

at many side replace the User property with:

public class Referral
{
    // ...
    public ApplicationUser Candidate { get; set; }
    public ApplicationUser Referrer { get; set; }
}

and correlate them with fluent API:

modelBuilder.Entity<ApplicationUser>()
    .HasMany(u => u.CandidateOf) // <--
    .WithRequired(r => r.Candidate) // <--
    .HasForeignKey(r => r.CandidateId)
    .WillCascadeOnDelete(false);

modelBuilder.Entity<ApplicationUser>()
    .HasMany(u => u.ReferrerOf) // <--
    .WithRequired(r => r.Referrer) // <--
    .HasForeignKey(r => r.ReferrerId);

The names of the navigation properties don't really matter as soon as you correlate them correctly.