Implementing "where not exists" with NHibernate QueryOver

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

select c.*
from Category c
where not exists (
    select *
    from CategoryProduct cp
    where cp.CategoryID = c.Id
    and cp.ProductID = 'DogFood'
)

In other words: "Give me all categories that doesn't contain dog food".

My initial thought was something like:

IEnumerable<Category> FindCategoriesWithoutProduct(Product product)
{
    return _session
        .QueryOver<Category>()
        .Where(c => c.Products.Contains(product))
        .List();
}

However, this makes NHibernate.Impl.ExpressionProcessor blow up with an "unrecognised metho开发者_如何学Pythond call" on System.Collections.Generic.ICollection<T>.Contains().

I assume there must be some other way to do this, probably involving an ICriterion, but my searches here and on Google have returned nothing useful.

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

Category aliasCategory = null;
CategoryProduct aliasCategoryProduct = null;

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

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

It works on my similar criteria.

Not tested, but something like this

IEnumerable<Category> FindCategoriesWithoutProduct(Product product)
{
    CategoryProduct categoryProductAlias = null;
    var subQuery = QueryOver.Of<CategoryProduct>(() => categoryProductAlias)   
        .Select(x => categryProductAlias.ID)
        .Where(() => categoryProductAlias.ProductID == "DogFood");

    Category categoryAlias = null;
    return _session
        .QueryOver<Category>(() => categoryAlias)
        .WithSubquery.WhereProperty(() => clientAlias.Id).NotIn(subQuery)
        .List();
}