nhibernate - Preventing multiple instance after inner join

Question

I have a small problem with multiple instances of the same object after a join to an other table. For testing I create one Store with two Products (ManyToMany-Relation). The following snippet hopefully describes my problem.

var preResult = _session.QueryOver<Store>().List(); // One store

Product productAlias = null;
var result = _session.QueryOver<Store>()
    .JoinAlias(s => s.Products, () => productAlias)
    .List();                                        // Two instances of the same store

I even think this behavior is correct but how can I prevent the multiple instances? Is it possible within the query?

---

Just for information why I need to make this unnecessary join: I want to extend the query according to different critirias, similar to this:

Product productAlias = null;
var query = _session.QueryOver<Store>().JoinAlias(s => s.Products, () => productAlias);
if (!string.IsNullOrWhiteSpace(criteria.ProductName))
{
    query.Where(Restrictions.On(() => productAlias.Name).IsInsensitiveLike(criteria.ProductName));
}

if (criteria.ProductType != null)
{
    query.Where(s => productAlias.Type == criteria.ProductType);
}

var result = query.List();

Here I ran into different problems, depending on the criterias.

Answer 1

Try using Transformers.DistinctRootEntity in your scenario to eliminate the cartesian product.

Product productAlias = null;
var query = _session.QueryOver<Store>()
                    .JoinAlias(s => s.Products, () => productAlias)

query = query.TransformUsing(Transformers.DistinctRootEntity);

var result = query.List();