One to One Relationship With Same Entity Type - FluentAPI

Question

Just a little concern on how to configure EF for a one to one relationship with same Entity which is a rare case for me. This requirement came to me and i was a bit skeptical on how to model this.

Here is the scenario,

A patient can have one partner and a partner can only belong to one patient. A partner is also a patient.

I have my model like this;

 public class Patient
 {
    public long Id { get; set; }

    public string FirstName { get; set; }

    public string LastName { get; set; }

    public EGender Gender { get; set; }

    public DateTime DateOfBirth { get; set; }

    public DateTime CreatedAt { get; set; }

    public long PartnerId { get; set; }

    public Patient Partner { get; set; }

    public EPatientType PatientType { get; set; }
 }

And my FluentAPI config like this, but not sure i got this right

      builder.HasOne(p => p.Partner)
            .WithOne(p => p.Partner) // Not sure what to do here
            .IsRequired(false)
            .HasForeignKey<Patient>(p => p.PartnerId)
            .OnDelete(DeleteBehavior.Restrict);

Any idea on how to model this on fluentAPI or how to proceed is appreciated...

Answer 1

[索引（“IX_UniqueParentId”，1，IsUnique = true）]

public long? PartnerId { get; set; }

Answer 2

Try to use:

builder.HasOne(p => p.Partner)
       .WithOne()
       .IsRequired(false)
       .HasForeignKey<Patient>(p => p.PartnerId);

It worked for me.