Programming to interfaces while mapping with Fluent NHibernate

Question

I have been whipped into submission and have started learning Fluent NHibernate (no previous NHibernate experience). In my project, I am programming to interfaces to reduce

Answer 1

I am having exactly the same issue. Unfortunately I have a valid reason for using entity interfaces; the entity model will be implemented in different ways and with different mappings per customer.

The entire model needs to be read-only, so interfaces are of the style:

public interface IAccount
{
    long AccountId { get; }
    IHouse House { get; }
}

public interface IHouse
{
    long HouseId { get; }
    HouseStatus Status { get; }
    IList Accounts { get; }
}

Concrete implementations then implement these with internal setters:

public class Account: IAccount
{
    public virtual long AccountId { get; internal set; }
    public virtual IHouse House { get; internal set; }
}

public class House: IHouse
{
    public virtual long HouseId { get; internal set; }
    public virtual HouseStatus Status { get; internal set; }
    public virtual IList Accounts { get; internal set; }
}

I have gone down the route of mapping to the concrete classes. All is fine until you create relations which return interfaces and need to be cast to concrete implementations.

HasMany(x => x.Accounts)

can become

HasMany(x => x.Accounts)

But there is no equivalent 'cast' for

References(x => x.House)

Mapping to the interfaces (the neater solution) throws up the problem mentioned above in that the Id must exist on the topmost class for setting and requires a setter on the interface.

public sealed class AccountMap : ClassMap
{
    public PokerPlayerMap()
    {
        Id(x => x.AccountId, "account_id");

        DiscriminateSubClassesOnColumn("Type").SubClass(s =>  
        {
            References(x => x.House);       
        });
    }
}

For now, my only solution is to add setters to all of the interface Id fields. Its a shame the Id can't exist inside a subclass or have its type cast from the interface.