NHibernate -How to conditionally load data from a column - nhibernate

Question

We are not using Fluent Nhibernate. We have a table with a blob column which we would like to load conditionally. We already have specified it as 'lazy' and lazy loading is working fine. Is there a way to not load data for that column at all on a certain condition ? (hence for the property in respective class)
For example, here is the mapping
<?xml version="1.0" encoding="utf-8"?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" namespace="Blah.blah.blah" assembly="Blah.blah">
<class name="MyDocument" table="HEAVY_DOCS">
<id name="Id" column="docnum" type="decimal"> </id>
<property name="docname" column="docname" />
<property name="details" column="details" />
<property name="doc_data" column="document_data" lazy="true" />
</class>
</hibernate-mapping>
and below is the code getting document
private IList<MyDocument> FetchDocuments(IList<string> docId, bool laodData)
{
if(!laodData)
{
docs = (from doc in Session.Query<MyDocument>()
where docId.Contains(doc.docnum)
select doc).ToList();
}
else
{
//if laodData is false dont load column document_data
}
return docs ;
}

Answer 1

The way, how to drive column selection by our code, is to use projections. Adjusted code could look like this:
if(!laodData)
{
docs = (from doc in Session.Query<MyDocument>()
where docId.Contains(doc.docnum)
select doc // complete object
).ToList();
}
else
{
docs = (from doc in Session.Query<MyDocument>()
where docId.Contains(doc.docnum)
select new MyDocument // in NHibernate world
{ // that would be called
docname= doc.docname, // projection
details = doc.details,
// no "doc_data" for LARGE document
Id = doc.Id,
}
).ToList();
}
With QueryOver the projections can profit from NHibernate built in powerful Result Transformers, which can fill even protected properties. Maybe see this custom transformer example for deep (relations including) transformations of QueryOver projections...