nhibernate saving a dictionary in a ternary relation

Class:

class Track
{
    ...
    public virtual IDictionary<People, Role> PeopleRoles { get; set; }
}

Mapping:

<class name="Track" ...>
   ...
   <map name="PeopleRoles" table="track_people_role">
   <key column="track_id"/>
   <map-key-many-to-many column="people_id" class="People"/>
   <many-to-many colum开发者_StackOverflow社区n="role_id" class="Role"/>
  </map>
</class>

When I execute the code below I can see the row inserted in track_people_role table as 47637,10,1

    Person p = PersonManager.GetById(10);
    Role pr = RoleManager.GetById(1);
    Track t = TrackManager.GetById(47637);

    t.PeopleRoles.Add(p, pr);
    TrackManager.Save(t);

after when I execute the previous with a different role I get "An item with the same key has already been added" error

    Person p = PersonManager.GetById(10);
    Role pr = RoleManager.GetById(2);
    Track t = TrackManager.GetById(47637);

    t.PeopleRoles.Add(p, pr);
    TrackManager.Save(t);

Any ideas how i can manage to insert the second row.

EDIT:

Mapping:

<class name="TrackPersonRole, App.Data" table="trackpeoplerole" lazy="true">
    <composite-id>
    <key-many-to-one name="Person" class="Person" column="people_id"/>
    <key-many-to-one name="Role" class="Role" column="role_id"/>
    </composite-id>
</class>

<class name="Track" ...>
 ...
 <bag name="TrackPeopleRoles">
     <key column="track_id"/>
     <one-to-many class="TrackPersonRole"/>
 </bag>
</class>


    TrackPersonRole tpr = new TrackPersonRole();
    tpr.Person = PersonManager.GetById(10);
    tpr.Role = RoleManager.GetById(2);
    entity.PeopleRoles.Add(tpr);
    TrackManager.SaveOrUpdate(entity);

generates the below update statement, instead of an insert.

UPDATE trackpeoplerole SET track_id = 47637 /* ?p0 */
WHERE people_id = 10 /* ?p1 */ AND role_id = 2 /* ?p2 */

The error message is correct: you are adding a duplicate key to a dictionary.

It does not even come from NHibernate - it's generated by the Dictionary class.

If a Track can have the same Person in more than one Role, you'll have to map the track_person_role table as an entity:

class Track
{
    ...
    public virtual ICollection<TrackPersonRole> PeopleRoles { get; set; }
}

class TrackPeopleRole
{
    public virtual Person Person { get; set; }
    public virtual Role Role { get; set; }
}

Mapping:

<class name="Track" ...>
  ...
  <bag name="TrackPeopleRoles">
    <key column="track_id"/>
    <one-to-many class="TrackPersonRole"/>
  </map>
</class>

There are more details regarding inverse and cascade, but start with this.