导航属性名称与属性类型不同时，NHibernate多对一/一对多外键如何处理？

Question

I'm using NHibernate/FluentNhibernate with AutoMapping configuration and I'm having troubles with foreign keys of some relationships. Especially those where the navigation property name is different from the the name of the type it is pointing to :

public class Country       
{
    public virtual string Code { get; set; }

    public virtual string Name { get; set; }

    public virtual Currency DefaultCurrency { get; set; }
}

public class Currency
{
    public virtual string Code { get; set; }

    public virtual decimal Rate { get; set; }

    public virtual IList<Country> Countries { get; set; }     
}

In the case of Country entity where the name of navigation property DefaultCurrency is different from the name Currency type. The automapping of NHibernate will guess that the Country table will have the following foreign key:

• DefaultCurrency_id : corresponding to the relation of Country.Currency

• Currency_id : corresponding to the relation of Currency.Countries

How to tell to the automapping that the relation Currency.Countries can be expressed with DefaultCurrency_id key, resulting to one key foreign only for the Country table:

• DefaultCurrency_id : corresponding to the relation of Country.Currency and Currency.Countries

Answer 1

You can specify any column name you want in the mapping.

For references:

References(x => x.Foo, "MyFooId")

For has-many:

HasMany(x => x.Foos)
    .KeyColumn("MyFooId")

For many-to-many:

HasManyToMany(x => x.Foos)
    .ChildKeyColumn("MyFooId")
    .ParentKeyColumn("MyFooId")

You can also use conventions, eg:

public class HasManyConventions : IHasManyConvention
{
    public void Apply(IOneToManyCollectionInstance target)
    {
        target.Key.Column(target.EntityType.Name + "Id");
    }
}