And I should also note: of course, using lazy="false" in the Institution class mapping (as in: <class name="Institution" lazy="false">) keeps the exception from being thrown...but I can't make this the default fix whenever I get a bug like this!
On Mar 15, 4:16 pm, SedulousTurtle <[email protected]> wrote: > Hi List, > > I'm responsible for looking at NHibernate as a potential DB solution > on our next product release -- but I'm having trouble getting my > prototype to work properly. In a few cases, I'm getting perplexing > behaviour associated with lazy loading and proxies. I suspect that > these are all occuring because I have some error in my understanding > of how these work. > > Here's my first problem. I'm encountering a > LazyInitializationException when my WebApp testing front end tries to > display a DataGrid with information about objects of type Instrument. > > ---------------- Application information ------------------ > The application manages electronic medical instruments in a hospital. > > Part of our object system is a heiarchy of parent/child relationships > (parent owns a collection of children; children have a reference to > their parent; I don't think either end is set inverse="true") > > Institution (e.g. Springfield Hospital) > Location (e.g. Emergency Room) > Instrument > > Institution and Location are effectively "virtual" classes (though > they're not explicitly marked as such); they each have 2 subclasses > that are used in the database. > > References in the source code to other objects such as > HealthCareSystem and Method are unimportant. > > ------------------------------------ Source Code > ------------------------------------------- > <Locations.aspx.cs> > ... > private void BindInstrumentGrid() > { > ... > > grInstr.DataSource = > Facade.InstLoc.GetInstruments(<various parameters>); > grInstr.DataBind(); > } > > <InstrumentFacade.cs> > ... > public IList GetInstruments(<various parameters>) > { > IList<Instrument> instrumentList; > ... > > using (ISession ses = NHibernateHelper.OpenSession()) > using (ses.BeginTransaction()) > { > instrumentList = ses.CreateQuery( > @"SELECT instr FROM Instrument AS instr > JOIN instr.Method AS md > JOIN md.Method AS meth > JOIN instr.Location AS loc > JOIN loc.Institution AS instit > JOIN instit.HCSystem AS hcs > WHERE meth.Name=:method_name > AND loc.Name=:location_name > AND instit.Name=:institution_name > AND hcs.Name=:healthcaresystem_name") > .SetString("method_name", methodName) > .SetString("location_name", asLocationName) > .SetString("institution_name", asInstName) > .SetString("healthcaresystem_name", > asHCSystemName) > .List<Instrument>(); > > foreach (Instrument i in instrumentList) > { > NHibernateUtil.Initialize(i.Location); > NHibernateUtil.Initialize(i.Location.Institution); > } > > ses.Transaction.Commit(); > } > return instrumentList.ToList(); > } > ... > ---------------------------------------------------------------------------------------------------- > > On application execution, when BindInstrumentGrid() executes > "grInstr.DataBind();" I get the following NHibernate exception: > "Initializing[TestRecordProto.Domain.Institution#2]-Could not > initialize proxy - no Session." > > I partially understand why I'm getting this error, because I'm seeing > weird behavior during NHibernateUtil.Initialize() when I run in debug > mode. Initially, i.Location is of type LocationProxy -- with its only > set property being "string Name". All other properties, including the > int ID, is uninitialized. But after "Initialize(i.Location)", I would > expect i.Location proxy would be replaced with a real object of type > Location. But it is not in fact replaced -- the reference is left as > a proxy, and its properties do not change! And of course then > "Initialize(i.Location.Institution)" can not really initialize the > Institution field -- because i.Location.Institution is null, because > i.Location is a proxy without instantiated properties! > > So I don't know what I'm doing wrong -- I'm supposed to call > Initialize() on the referenced objects that I'll need to access after > the session is closed -- and yet Initialize() isn't solving the > problem for me. Why does this happen? > > The information in the database all looks correct, with the correct > links between these objects. I have 1 record saved of type > Instrument, which is linked by foreign key to a valid Location, which > is linked by foreign key to a valid Institution. > > Thank you in advance. -- You received this message because you are subscribed to the Google Groups "nhusers" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/nhusers?hl=en.
