EF Code First cascade delete doesn't work - entity-framework

Question

I have 4 tables:
User table
public enum SEX { Male, Female }
public abstract class User
{
public int UserID { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string Phone { get; set; }
public SEX Sex { get; set; }
}
Doctor table inherites from User
[Table("Doctor")]
public class Doctor : User
{
public string Department { get; set; }
public string Occupation { get; set; }
public string CabinetNumber { get; set; }
public virtual List<Treat> Treats { get; set; }
}
Patient table inherites from User
[Table("Patient")]
public class Patient : User
{
public int InsuranceNumber { get; set; }
public int CardNumber { get; set; }
public virtual List<Treat> Treats { get; set; }
}
public class Treat
{
public int TreatId { get; set; }
public int DoctorUserId { get; set; }
public int PatientUserId { get; set; }
public virtual Doctor Doctor { get; set; }
public virtual Patient Patient { get; set; }
}
public class HospitalContext: DbContext
{
public HospitalContext() : base("DBConnectionString") {
Database.SetInitializer(new DropCreateDatabaseIfModelChanges<HospitalContext>());
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Treat>()
.HasRequired(x => x.Doctor)
.WithMany( x => x.Treats)
.HasForeignKey( x => x.DoctorUserId)
.WillCascadeOnDelete(true);
modelBuilder.Entity<Treat>()
.HasRequired(x => x.Patient)
.WithMany( x => x.Treats)
.HasForeignKey( x => x.PatientUserId)
.WillCascadeOnDelete(true);
base.OnModelCreating(modelBuilder);
}
public DbSet<User> Users { get; set; }
public DbSet<Treat> Treats { get; set; }
}
I have found much answers here but no one from them works. I have spend a few hours trying to make it work. I know that Entity Framework must enable cascade delete when there is one-to-many relation, but it didn't

Answer 1

Entity Framework doesn't apply cascade deletion with TPT (Table Per Type) inheritance. You can solve this with Code Fist migrations:
CreateTable(
"dbo.Treats",
c => new
{
TreatId = c.Int(nullable: false, identity: true),
DoctorUserId = c.Int(nullable: false),
PatientUserId = c.Int(nullable: false),
})
.PrimaryKey(t => t.TreatId)
.ForeignKey("dbo.Doctor", t => t.DoctorUserId, cascadeDelete: true)
.ForeignKey("dbo.Patient", t => t.PatientUserId, cascadeDelete: true)
.Index(t => t.DoctorUserId)
.Index(t => t.PatientUserId);
The important part is cascadeDelete: true. You have to manually add it after migration code generation. After that you will have cascade deletion in your database:
FOREIGN KEY ([DoctorUserId]) REFERENCES [dbo].[Doctor] ([UserID]) ON DELETE CASCADE,
FOREIGN KEY ([PatientUserId]) REFERENCES [dbo].[Patient] ([UserID]) ON DELETE CASCADE