Unique key on multiple columns where one is a foreign key - how to ?

Hi,

I have a DictionaryElement class like:

public class DictionaryElement : BaseEntity

{
    [DomainSignature]
    public virtual string Alias { get; set; }
    public virtual Dictionary Dictionary { get; set; }
    public virtual string Name { get; set; }
}

I'm trying to set unique key on two colums: alias and DictionaryFk (conventions from SharpArch by default add "Fk" to foreign key columns).

I define automappings like:

public class DictionaryElementMap : IAutoMappingOverride

{
    public void Override(AutoMapping<DictionaryElement> mapping)
    {
        const string uniqueForDictionaryKeyName = "uniqueForDictionary";
        mapping.Map(element => element.Alias).Index(uniqueForDictionaryKeyName);
        mapping.Map(element => element.Dictionary).Index(uniqueForDictionaryKeyName);
    }
}

but that results in an error when I try to execute schema:

• Database was not configured through Database method.

----> NHibernate.MappingException : Could not compile the mapping document: (XmlDocument) ----> NHibernate.MappingException : Could not determine type for: Common.Data.Dictionaries.Dictionary, Common.Data, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null, for columns: NHibernate.Mapping.Column(Dictionary)

And mappings (dumped to .hbm) look like:

<property name="Alias" type="System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
  <column name="Alias" index="uniqueForDictionary" />
</property>
<property name="Dictionary" type="Common.Data.Dictionaries.Dictionary, Common.Data, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null">
  <column name="Dictionary" index="uniqueForDictionary" />
</property>
<property name="Name" type="System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
  <column name="Name" />
</property>

which is totaly wrong for "Dictionary".

I noticed that the same think works when I would like to set this unique key on two columns that are not foreign keys, like for example name and alias. then mapping looks like:

  <column name="Alias" index="uniqueForDictionary" />
</property>
<property name="Name" type="System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
  <column name="Name" index="uniqueForDictionary" />
</property>
<many-to-one class="Common.Data.Dictionaries.Dictionary, Common.Data, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" name="Dictionary">
  <column name="DictionaryFk" />
</many-to-one>

and is correct.

Can anybody help me with any suggestions?
thanks,
Łukasz Podolak