[NHibernate] A correct way to load entities by Id list when Id is not mapped

Question

I have the following code

string idName = builder.IdentifierName;
Disjunction disjunction = Restrictions.Disjunction();
IList ids = new ArrayList(entityInfos.Length);
foreach (var entityInfo in entityInfos)
{
    ids.Add(entityInfo .Id);
}
disjunction.Add(Restrictions.In(idName, ids));
criteria.Add(disjunction);
criteria.List();

(I haven't written it, it's simplified code from NHibernate.Search)

Value of idName is correct ("Id").

In my mapping I do not have Id mapped to an entity property, it is DB-only:

<id column="Id" type="int">
  <generator class="native" />
</id>

When I run the code, it throws an exception:

[QueryException: could not resolve property: Id of: MyType]
   NHibernate.Persister.Entity.AbstractPropertyMapping.ToType(String propertyName) +326
   NHibernate.Loader.Criteria.CriteriaQueryTranslator.GetTypeUsingProjection(ICriteria subcriteria, String propertyName) +416
   NHibernate.Criterion.InExpression.AssertPropertyIsNotCollection(ICriteriaQuery criteriaQuery, ICriteria criteria) +41
   NHibernate.Criterion.InExpression.ToSqlString(ICriteria criteria, ICriteriaQuery criteriaQuery, IDictionary`2 enabledFilters) +49
   NHibernate.Criterion.Junction.ToSqlString(ICriteria criteria, ICriteriaQuery criteriaQuery, IDictionary`2 enabledFilters) +448
   NHibernate.Loader.Criteria.CriteriaQueryTranslator.GetWhereCondition(IDictionary`2 enabledFilters) +354
   NHibernate.Loader.Criteria.CriteriaJoinWalker..ctor(IOuterJoinLoadable persister, CriteriaQueryTranslator translator, ISessionFactoryImplementor factory, ICriteria criteria, String rootEntityName, IDictionary`2 enabledFilters) +516
   NHibernate.Loader.Criteria.CriteriaLoader..ctor(IOuterJoinLoadable persister, ISessionFactoryImplementor factory, CriteriaImpl rootCriteria, String rootEntityName, IDictionary`2 enabledFilters) +220
   NHibernate.Impl.SessionImpl.List(CriteriaImpl criteria, IList results) +364
   NHibernate.Impl.CriteriaImpl.List(IList results) +63
   NHibernate.Impl.CriteriaImpl.List() +46

What is the correct way to create a restriction and criteria so that I can search by Id even if it is not mapped?

Answer 1

Try IdEq instead. It needs another Disjunction.

Disjunction idsRestriction = Restrictions.Disjunction();
entityInfo
  .Select(x => x.Id)
  .ToList()
  .ForEach(id => idsRestriction.Add(Restriction.IdEq(id)));
disjunction.Add(idsRestriction);

Note: this will produce something like (id = 1 OR id = 2 OR id = 3 ...) instead of (id IN (1, 2, 3).

Not hundred percent sure if it works, but it should.

Answer 2

You can use IdEq, or use the keyword "id" (all lower case) to refer to the primary key