Should Domain Entities be exposed as Interfaces or as Plain Objects?

Question

Should Domain Entities be exposed as Interfaces or as Plain Objects ?

The User Interface :

public interface IUser
{
    string FirstName { get; set; }
           


        

Answer 1

Plain objects, unless there's a common interface for an implementation that can change. That's what interfaces are for. Value classes like Money or Address don't fall into that category.

Your example interface has no behavior whatsoever beyond getter/setter. That's not what interfaces are for.