Should business objects contain objects or references?

Question

Should a business object contain a reference to other objects (as in the id field references another database record) or should it have an instance of the actual objects.

For example:

public class Company
{
    public int Id { get; set; }
    public CompanyStatus Status { get; set; }
}

or

public class Company
{
    public int Id { get; set; }
    public int Status { get; set; }
}

Answer 1

If you're talking about C#, then aggregating an object means you're storing a reference to it.

Answer 2

It depends on the data. Some data should be stored as a copy of the original object, some should be a reference.

Answer 3

From my understanding, it should contain references to interfaces, not concrete classes.

public class Company
{
    public int Id { get; set; }
    public ICompanyStatus Status { get; set; }
}

Assuming that the concrete implementation of CompanyStatus in your example was a class and not an enum.

Answer 4

When creating Business Layer objects in an OO fashion, you should be using objects directly.

In your example, does int Status refers to the Id of a CompanyStatus object stored somewhere? In that case, it really feels like that's more of a data layer concern. It is usually best to avoid mixing your data layer with your business layer.