How to map IDictionary in Fluent NHibernate

Question

I have an class with an IDictionary on it.

Answer 1

Map the book.name as the key instead of the nickname.

Answer 2

I have a working example, this should make it clear to you.

Classes:

public class Customer : Entity
{        
    public IDictionary<string, Book> FavouriteBooks { get; set; }
}

public class Book : Entity
{
    public string Name { get; set; }
}

And then the map:

HasManyToMany<Book>(x => x.FavouriteBooks)
            .Table("FavouriteBooks")                
            .ParentKeyColumn("CustomerID")
            .ChildKeyColumn("BookID")
            .AsMap<string>("Nickname")                
            .Cascade.All();

Resulting xml:

<map cascade="all" name="FavouriteBooks" table="FavouriteBooks" mutable="true">
  <key>
    <column name="`CustomerID`" />
  </key>
  <index type="System.String, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
    <column name="`Nickname`" />
  </index>
  <many-to-many class="Domain.Book, Domain, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null">
    <column name="`BookID`" />
  </many-to-many>
</map>

Generated SQL:

create table "Customer" (
    "Id"  integer,
   "FirstName" TEXT,
   primary key ("Id")
)

create table FavouriteBooks (
    "CustomerID" INTEGER not null,
   "BookID" INTEGER not null,
   "Nickname" TEXT not null,
   primary key ("CustomerID", "Nickname")
)

create table "Book" (
    "Id"  integer,
   "Name" TEXT,
   primary key ("Id")
)