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Asked: 2026-05-18T06:54:36+00:00

I have a mapping that looks like this: <class name=Record> <map name=Values> <key column=RecordFK/>

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I have a mapping that looks like this:

  <class name="Record">
    <map name="Values">
      <key column="RecordFK"/>
      <index column="FieldFK"/>
      <element column="Value"/>
    </map>
  </class>

Translating this to English: a Record maps Fields to Values. In HQL, I can query this map, as follows:

from Record rec where rec.Values[:fieldFK] = :value

Is it possible to recreate this query using the new Linq provider in NHibernate 3.0 instead of HQL? I tried the following code without success:

   var records = session.Query<Record>()
                    .Where(rec => rec.Values[field.Key] == "foo");

This produced an error when NHibernate tried to interpret the dictionary accessor:

System.NotSupportedException:
System.String get_Item(System.Int32)

Is there some way to “teach” NHibernate how to turn this C# expression into SQL?

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1 Answer

  1. Editorial Team

    NHibernate 3 does have a way to extend the provider to allow more expressions, check http://fabiomaulo.blogspot.com/2010/07/nhibernate-linq-provider-extension.html

    However, this looks like something that should be supported. My suggestion is that you create a ticket at http://jira.nhforge.org with a failing test case.

    If you’re feeling like doing a little bit more, you can dive into https://nhibernate.svn.sourceforge.net/svnroot/nhibernate/trunk/nhibernate/src/NHibernate/Linq and create a patch. That will make things faster.

    Update (2010-12-04): My patch has been merged into the trunk. This scenario is now supported (you can compile from source, or wait a few days for the final release)

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