TPT inheritance in entity framework code first

Question

by using Table per Type (TPT) inheritance in Entity Framework codefirst we can create foreign keys like this :

    public abstract class Person
{

    public int id { get; set; }
    public string Name { get; set; }
    public string Family { get; set; }

}


[Table("Doctors")]

public class Doctor : Person
{
    public string ExpertTitle { get; set; }
}
[Table("Notes")]
public class Note : Doctor
{
    public string Content { get; set; }
}

in above code In addition to the creating Doctors table and relating that with Persons table, we could create Note table and create 1-to-Many relation between Doctors Table and that.

but is that standard to create all foreign keys using inheritance instead of using virtual properties like what you see bellow?!

public class Doctor : Per
{
    public string ExpertTitle { get; set; }

    public virtual ICollection<Note> Notes { get; set; }
}

public class Note : Doctor
{
    public string Content { get; set; }
    public virtual Doctor Doctor { get; set; }
}

Does it make sense to derive Note from Doctor? I would model your classes logically and independently from the ORM. You wouldn't use inheritance just for creating a relationship. — user2697817
Yes you'r right ....its just a sample code ...my main question is this:is that true to create all foreign keys using inheritance instead of using virtual properties? — Iman Salehi
No, you would definitely not want to do this. Also, you can only create 1-2-1 relationships this way. — user2697817

Shimmy Weitzhandler Shimmy Weitzhandler · Accepted Answer · 2017-05-03T07:07:58

You'd only want to derive from Doctor, when you need to expand the Doctor type by adding to it additional properties, let's say Surgeon.

In your case, whether you want to attach a single or multiple notes to a doctor, is merely another property to ANY type of doctor.

So you should wither add a nullable/non-nullable string property or complex type Note in the Doctor type for a single note, or as you suggested yourself, a collection of Note each having its own ID.

TPT inheritance in entity framework code first

2 Answers