Question

I’m using <dynamic-component> elements to provide end-users the capacity to extend the functionality of our product by adding fields to the database.

A simplified version of our mapping is:

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" namespace="Caselle.Am0.DTO" assembly="Caselle.Am0.DTO" schema="dbo">
  <class name="Asset" table="[tblAsset]" lazy="true">
    <id name="ID" column="ID" type="Int32">
      <generator class="native" />
    </id>
   <property name="AssetNumber" column="[AssetNumber]" type="long" not-null="true" />
   <dynamic-component insert="true" update="true" name="UserDefinedFields" />
   <many-to-one name="Classification" column="tblClassificationID" class="Lib.DTO.Classification, Lib.DTO" cascade="none" />
 </class>

<class name="Classification" table="[tblClassification]" lazy="true">
  <id name="ID" column="ID" type="Int32">
    <generator class="native" />
  </id>
  <property name="Name" column="[Classification]" type="String" not-null="true" length="20" />
  <dynamic-component insert="true" update="true" name="UserDefinedFields" />
  <set name="Assets" table="tblAsset" lazy="true" cascade="all-delete-orphan" inverse="true">
    <key column="tblClassificationID"/>
    <one-to-many class="Lib.DTO.Asset, Lib.DTO"/>
</hibernate-mapping>

The classes look something like this:

public class Asset
{
  public virtual long AssetNumber{get; set;}
  public Classification Classification {get; set;}
  public virtual IDictionary UserDefinedFields {get; set;}
} 

public class Classification
{
  public virtual string Name {get; set;}
  public virtual ICollection<Asset> Assets {get; private set;}
  public virtual IDictionary UserDefinedFields {get; set;}
}

The problem I’m running into is that now users want to use our filtering tools on their custom fields, and I get a QueryException(Could not resolve property ‘X’) when I run the following query:

var query = session.CreateCriteria<Asset>()
            .Create Alias("c", "Classification")
            .Add(Restrictions.Eq(Projections.Property("c.X"), "value")
            .ToList<Asset>();

Is it possible to do this kind of a projection? How else might I write this query (I really like the Criteria API, since I’m generating this query on the fly, but if I have to work some other way…)?

Answer 1

I don’t think you want to use the projection there. Try swapping out

.Add(Restrictions.Eq(Projections.Property("c.X"), "value")

for

.Add(Restrictions.Eq("c.UserDefinedFields.X", "value")