IDictionary with composite element mapping

Hi there,

i have these 2 classes:

public class Category
    {
        IDictionary<string, CategoryResorce> _resources;
    }

public class CategoryResource
    {
        public virtual string Name { get; set; }
        public virtual string Description { get; set; }
    }

and this is xml mapping

<generator class="identity"/>

  <key column="EntityID" />
  <index column="LangCode" type="string"/>

  <composite-element class="Aca3.Models.Resources.CategoryResource">
    <property name="Name" column="Name" />
    <property name="Description" column="Description"/>
  </composite-element>

and i'd like to write it with Fluent. I found something similar and i was trying with this code:

HasMany(x => x.Resources)

            .AsMap<string>("LangCode")
            .AsIndexedCollection<string>("LangCode", c => c.GetIndexMapping())
            .Cascade.All()
            .KeyColumn("EntityID");

but i dont know how to map the CategoryResource entity as a composite element inside the Category element.

Any advice ?

thanks