有没有更优雅的方法来指定多个相同性质的一对多关系？

Question

I'm having trouble trying to create the following entities relations. My code has the classes Shop and Person , and both have multiple Phones . My first implementation was something like this:

public class Person {
  public int Id;
  public string Name;
  public virtual ICollection<Phone> Phones;
}

public class Shop {
  public int Id;
  public string Name;
  public virtual ICollection<Phone> Phones;
}

public class Phone {
  public int Id;
  public string AreaCode;
  public string Number;

  public int? ShopId;
  public virtual Shop Shop;

  public int? PersonId;
  public virtual Person Person;
}

and the model builder like

modelBuilder.Entity<Person>()
  .HasMany(p => p.Phones)
  .WithOptional(p => p.Person)
  .HasForeignKey(p => p.PersonId);

modelBuilder.Entity<Shop>()
  .HasMany(p => p.Phones)
  .WithOptional(p => p.Shop)
  .HasForeignKey(p => p.ShopId);

My doubt here is: can I model it or change anything in my classes so when I'm handling the phones I don't have to keep checking if they are related to a Shop or a Person ?

Answer 1

I would suggest the next scheme:

public class Owner
{
  public int Id;
  public string Name;
  public virtual ICollection<Phone> Phones;
  public abstract SendMessage(Phone phone);
}

public class Person : Owner 
{
  public override SendMessage(Phone phone)
  {
   ...
  }

}
public class Shop : Owner 
{
  public override SendMessage(Phone phone)
  {
   ...
  }
}

public class Phone {
  public int Id;
  public string AreaCode;
  public string Number;

  public int? OwnerId;
  public virtual Owner Owner;
}

So you haven't two entities with duplicating fields and, as npinti mentioned, you delegate messaging function to the corresponding entity.

Answer 2

To add a little bit more context to my comment, the way I would go about it (with the information currently at hand) would be as follows:

1. I would create an interface, IMessageSender , which has 1 method: SendMessage(Phone destination) .
2. Have the Shop and Person class implement that interface. In the implementation of the method you would then have your logic which, from the comments, should differ from Person and Shop .
3. In the location where you want to send the message, simply iterate over the object and invoke SendMessage . This will, in turn, delegate the logic of the construction of the message to the appropriate class.