Code First TPT Modeling where item can be multiple derived types

Question

What is the best way to model the following kind of relationship in Code First?

abstract Person

Student: Person

Teacher: Person

Researcher: Person

...many more...

Where a person is one OR MORE derived types.

I like the idea of TPT but not sure that it is appropriate when the relationship is such that a person can be a student and a researcher.

Answer 1

You can use composition to model the scenario. This can be configured with shared primary key mapping where all the classes correspond to unique tables.

public class Person
{
    public int Id { get; set; }

    public string Name { get; set; }
}

public abstract class Role
{
    public int PersonId { get; set; }

    public virtual Person Person { get; set; }
}

public class Student : Role
{

}

public class Teacher : Role
{

}

public class RoleContext : DbContext
{
    public DbSet<Student> Students { get; set; }

    public DbSet<Teacher> Teachers { get; set; }

    public DbSet<Person> Persons { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Student>().ToTable("Student");
        modelBuilder.Entity<Student>().HasKey(s => s.PersonId);
        modelBuilder.Entity<Student>().HasRequired(s => s.Person).WithOptional();

        modelBuilder.Entity<Teacher>().ToTable("Teacher");
        modelBuilder.Entity<Teacher>().HasKey(t => t.PersonId);
        modelBuilder.Entity<Teacher>().HasRequired(t => t.Person).WithOptional();
    }
}