NHibernate LINQ query throws error "Could not resolve property" - linq

Question

I'm testing out using LINQ with NHibernate but have run into some problems with resolving string.length. I have the following
public class DC_Control
{
public virtual int ID { get; private set; }
public virtual string Name { get; set; }
public virtual bool IsEnabled { get; set; }
public virtual string Url { get; set; }
public virtual string Category { get; set; }
public virtual string Description { get; set; }
public virtual bool RequireScriptManager { get; set; }
public virtual string TriggerQueryString { get; set; }
public virtual DateTime? DateAdded { get; set; }
public virtual DateTime? DateUpdated { get; set; }
}
public class DC_ControlMap : ClassMap<DC_Control>
{
public DC_ControlMap()
{
Id(x => x.ID);
Map(x => x.Name).Length(128);
Map(x => x.IsEnabled);
Map(x => x.Url);
Map(x => x.Category);
Map(x => x.Description);
Map(x => x.RequireScriptManager);
Map(x => x.TriggerQueryString);
Map(x => x.DateAdded);
Map(x => x.DateUpdated);
}
}
private static ISessionFactory CreateSessionFactory()
{
return Fluently.Configure()
.Database(FluentNHibernate.Cfg.Db.MsSqlConfiguration.MsSql2008)
.Mappings(m => m.FluentMappings.AddFromAssembly(Assembly.GetExecutingAssembly()))
.ExposeConfiguration(c => c.SetProperty("connection.connection_string", "CONNSTRING"))
.ExposeConfiguration(c => c.SetProperty("proxyfactory.factory_class", "NHibernate.ByteCode.Castle.ProxyFactoryFactory,NHibernate.ByteCode.Castle"))
.BuildSessionFactory();
}
public static void test()
{
using (ISession session = sessionFactory.OpenSession())
{
var sqlQuery = session.CreateSQLQuery("select * from DC_Control where LEN(url) > 80").AddEntity(typeof(DC_Control)).List<DC_Control>();
var linqQuery= session.Linq<DC_Control>().Where(c => c.Url.Length > 80).ToList();
}
}
In my test method I first try and perform the query using SQL, this works just fine. Then I want to do the same thing in LINQ, and it throws the following error:
NHibernate.QueryException: could not resolve property: Url.Length of: DC_Control
I've searched alot for this "could not resolve property" error, but I can't quite figure out, what this means. Is this because the LINQ implementation is not complete? If so it's a bit disappointing coming from Linq2Sql where this would just work.
I also tried it setting up the mapping with a hbm.xml instead of using FluentNHibernate but it produced teh same error.

Answer 1

String.Length projections are not supported by the old (2.x) Linq provider.
The new Linq provider in NHibernate 3.x is integrated; you don't have to download anything extra.
The new extension method is session.Query instead of session.Linq; if you're using the latter, you are still using the old provider.