Implementing “where not exists” with NHibernate QueryOver

Question

Using the new QueryOver API in NHibernate, I need to do something equivalent of:

select c.*
from Category c
where not exists (
    select *
             


        

Answer 1

I'm just running in the same problem, and possible solution is:

Category aliasCategory = null;
CategoryProduct aliasCategoryProduct = null;

var qcp = QueryOver.Of(() => aliasCategoryProduct)
          .Where(() => aliasCategoryProduct.ProductID == "DogFood")
          .Where(() => aliasCategory.Id == aliasCategoryProduct.CategoryID)
          .DetachedCriteria;

return _session.QueryOver(() => aliasCategory)
               .Where(Subqueries.NotExists(qcp));

It works on my similar criteria.