Lazy loading a portion of a record with NHibernate.

Question

I'm not sure how to explain this. So here goes...

I'm trying to fit the method for lazy loading blobs as described here but I'm stuck with only one table.

I have a schema (fixed, in a legacy system) which looks something like this:

MyTable
   ID int
   Name char(50)
   image byte

This is on Informix, and the byte column is a simple large object. Now normally I would query the table with "SELECT ID, Name, (image is not null) as imageexists..." and handle the blob load later.

I can construct my object model to have two different classes (and thus two different map definitions) to handle the relationship, but how can I "fool" nhibernate into using the same table to show this one-to-one relationship?

Answer 1

Short answer: you can't.

You either need to map it twice or (my preference) create a DTO that has the fields you want. In HQL you'd do something like:

select new MyTableDTO(t.ID, t.name) from MyTable t