DBFirst one to one or zero

public Patient(){
    {
        Appointments = new HashSet<Appointment>();
        MedicalCards = new HashSet<MedicalCard>();
    }

public int Id { get; set; }
public string? Lastname { get; set; }
public string? Firstname { get; set; }
public string? Middlename { get; set; }
public string? Phone { get; set; }
public string? Address { get; set; }
public bool? Gender { get; set; }
public int? Medcard { get; set; }

public virtual MedicalCard? MedcardNavigation { get; set; }
public virtual ICollection<Appointment> Appointments { get; set; }
public virtual ICollection<MedicalCard> MedicalCards { get; set; }

public partial class MedicalCard
{
    public MedicalCard()
    {
        MedicalReports = new HashSet<MedicalReport>();
        Patients = new HashSet<Patient>();
    }
public int Id { get; set; }
public int Patient { get; set; }
public DateTime? Issued { get; set; }

public virtual Patient PatientNavigation { get; set; } = null!;
public virtual ICollection<MedicalReport> MedicalReports { get; set; }
public virtual ICollection<Patient> Patients { get; set; }
}