Trying to avoid multiple sub-types in a class structure

Question

I have two abstract classes Business & Person. The problem is that I have a customer type that can be either a Business or a Person. Is there a way to model this so that I don't have both CustomerBusiness and CustomerPerson classes? Multiple inheritance isn't an option as this is C#. I've been looking at this so long I can't see the forest for the trees.

public abstract class Business {
  public string Name { get; set; }
}

public abstract class Person {
  public string FirstName { get; set; }
  public string LastName { get; set; }
  public string MiddleName { get; set; }
  public DateTime? BirthDate { get; set; }
  public string Comments { get; set; }
}

public class CustomerBusiness : Business, CustomerRoles {
  public bool BillTo { get; set; }
  public bool ShipTo { get; set; }
  public bool DeliverTo { get; set; }
  public EntityType Type { get; set; }
}

public class CustomerPerson : Person, CustomerRoles {
  public bool BillTo { get; set; }
  public bool ShipTo { get; set; }
  public bool DeliverTo { get; set; }
  public EntityType Type { get; set; }
} 

public interface CustomerRoles {
  bool BillTo { get; set; }
  bool ShipTo { get; set; }
  bool DeliverTo { get; set; }
}

score 2 · Accepted Answer · edited May 23 '17 at 12:20

2

You could prefer composition over inheritance having the Business and Person classes "have a" ICustomerRoles instead of "is a" ICustomerRoles.

public class Business
{
    public string Name { get; set; }

    public ICustomerRoles CustomerRoles { get; set; }
}

public class Person
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string MiddleName { get; set; }
    public DateTime? BirthDate { get; set; }
    public string Comments { get; set; }

    public ICustomerRoles CustomerRoles { get; set; }
}

edited May 23 '17 at 12:20

Community

1
1

answered Feb 24 '12 at 20:49

Ed Chapel

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Thanks Ed, I'm starting to see your point. I need to clarify that I think I need to keep the Business and Person classes abstract as there will be other classes that will always have the Business and Person property sets. Examples are: Supplier, Division, Department, etc... – Chris Feb 27 '12 at 15:27
I'm not sure I'll be able to use this method due to other constraints (not in my original question) in this project but this solution is the best answer I've found so far. Thanks, Ed. – Chris Feb 28 '12 at 13:04

score 1 · Answer 2 · answered Feb 24 '12 at 16:55

I would say that you have your heirarchy in the wrong order. Customer should be a base class and then Business and Person should be implementations of the Customer class. I'm sure there are more attributes of a Customer that are common to all types of Customer other than those in the CustomerRoles interface.

I would have thought there would be things like CustomerCode etc. Also you could state that all customers have a Name property, and it's up to the getter in each sub class to return the appropriate value. As in a Business would have a single property called Name, whereas a person would have each of FirstName, MiddleName, Surname and also a Name property that would concatenate these in some way.

Tobsey, I tried your approach but I ran into trouble when I needed to inherit the Business properties into another entity much like Customer. Do you have an example implementation you can show me? Maybe I'm not interpreting your answer properly. — Chris, Feb 27 '12 at 15:29

Trying to avoid multiple sub-types in a class structure

2 Answers2