ONE (Person) to MANY (PersonTypes) in Code first does not create relationship in DB

Question

I have a person object

 public Person {
    public string FullName { get; set;  }
    public DateOfBirth DateOfBirth { get; set; }
    public ICollection<PersonTypeLookup> PersonTypes {get; set;} 
 }

I have a set of pre determined PersonTypeLookup types.

    public PersonTypeLookup(int id, string code, string displayName )
    {
        id = id;
        this.Code = code;
        this.DisplayName = displayName;
        
    }

I want a person to be many different Person Types so how can a ONE (person) have MANY (personTypeLookups) how can this be done,

public void Configure(EntityTypeBuilder<Person> configuration)
    { 
        ....
        configuration.HasMany(i => i.PersonTypes).WithOne().OnDelete(DeleteBehavior.Cascade);
        ....
    }

Ive tried adding the above to Person config, but when i build my DB using code first there is no link set up between the two tables in the database, I need this info ?

Answer 1

Can a single person be of multiple types? If not, than this is a one-to-many relationship, but the other way around. If yes, than this is a many-to-many relationship.

One-to-many design:

public class Person {
  public int Id { get; set; }
  public string FullName { get; set;  }
  public DateOfBirth DateOfBirth { get; set; }
  public int PersonTypeId { get; set; }
  public PersonType PersonType { get; set;} 
}

public class PersonType {
  public int Id { get; set; }
  public string Code { get; set; }
  public string DisplayName { get; set; }
  public virtual ICollection<Person> Persons { get; set; }
}

Many-to-many design:

public class Person {
  public int Id { get; set; }
  public string FullName { get; set;  }
  public DateOfBirth DateOfBirth { get; set; }
  public virtual ICollection<PersonType> PersonTypes { get; set;} 
}

public class PersonType {
  public int Id { get; set; }
  public string Code { get; set; }
  public string DisplayName { get; set; }
  public virtual ICollection<Person> Persons { get; set; }
}