Question

Let’s say I have the following two classes:

public class Person
{
    public string Name { get; set; }
    public string Address { get; set; }
}
public class Customer: Person
{
    public string CustomerNumber { get; set; }
    public string PaymentTerms { get; set; }
}

Now, if I have a person that I want to make a customer, I have, to the best of my knowledge, three options, and I’m hoping for advice on which is the best and on any other options, maybe using the new dynamics stuff in C#4.

I can add a constructor or property to Customer that takes a Person and assigns values to the base class, e.g.

public Customer(Person person)
{
    base.Name = person.Name;
    base.Address = person.Address;
}

or I can implement an untidy set accessor like this:

public Person Person
{
    set
    {
        Name = value.Name;
        Address = value.Address;
    }
}

or I can aggregate Person into Customer like this:

public class Customer
{
    public Person Person { get; set; }
    public string CustomerNumber { get; set; }
    public string PaymentTerms { get; set; }
}

The last is to me the neatest, except for always having to e.g. access Customer.Person.Name, instead of just Customer.Name.

Answer 1

I’d either use the constructor, or maybe a factory method, like

public static Customer CreateFromPerson(Person person)
{
    return new Customer(){ Name = person.Name }//etc...
}

I don’t like the setter as you’re not actually setting the ‘Person’ on a customer, and I don’t like the last option because it leads to a Law of Demeter (LOD) violation when you access the person through the customer (customer.person.name etc).