Fluent Nhibernate Mapping Multiple Join

Question

I am somewhat of an Nhibernate newbie and I have been researching but am unable to figure out how to accomplish what I want using an Nhibernate mapping.

I have the following tables for my objects

• Domains
• Companies
• Dealers

Domains can have many Companies and Companies can belong to many Domains. Companies have many Dealers but Dealers only belong to one Company. I would like a mapping for my Domains to generate a list of all the Dealers that belong to it, via the Companies.

I have a join table called CompanyDomains (with columns CompanyID and DomainID) that maintains a many-to-many relationship between Companies and Domains. This table is currently NOT mapped in my Nhibernate setup...I just join on it with a HasManyToMany in my Domain map. The Dealers table has a column with the CompanyID.

The results I want are easily attained with an SQL query:

SELECT * FROM Dealers
JOIN Companies on Companies.ID = Dealers.CompanyID
JOIN CompanyDomains on Companies.ID = CompanyDomains.CompanyID
WHERE DomainID = 1

This gives me all Dealers assigned to the Domain.

My question is, I want a List of Dealers in my Domain Mapping for this. How do I map that with Nhibernate?

If I have overlooked this solution elsewhere, please point me in the right direction, otherwise I appreciate any help you can provide.

Thanks! Erick

Answer 1

A possible solution would be to map a Dealers collection for a company with HasMany and add a convenience property to Domain :

public class Domain
{
    ...
    public virtual IList<Company> Companies { get; private set; }
    public IList<Dealer> Dealers 
    { 
        get { return Companies.SelectMany(x => x.Dealers).Distinct(); }
    }
}

public class Company
{
    ...
    public virtual IList<Domain> Domains { get; private set; }
    public virtual IList<Dealer> Dealers { get; private set; } 
}

public class Dealer
{
    ...
    public virtual Company Company { get; private set; }
}

As there is no immediate relationship between Dealer and Domain I don't think you can map it directly.