Mapping using an intermediate join table with 2 primary keys

How can I fluently map 2 entities that are joined together using a "join" table (it has 2 primary keys).

My entities:

Users
Roles

Then the 'join' table looks like:

RolesUsers
  RoleId
  UserId

So I wan开发者_运维百科t to query like this:

user.Roles

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In Fluent NHibernate this is achieved by using HasManyToMany in your mapping. Ex: (User mapping)

 HasManyToMany(x => x.Roles)
                .Table("RolesUsers")
                .ParentKeyColumn("UserId")
                .ChildKeyColumn("RoleId")
                .Cascade.All()
                .Inverse()