C# NHibernate with Spring LazyInitializationException when using the data

I'm working on an NHibernate project, and where I had trouble loading collections earlier (http://stackoverflow.com/questions/4213506/c-hibernate-criteria-loading-collection), I now have problems using data.

I'm using C# in combination with the NHibernate and Spring.Net framework, and I get an LazyInitializationException after I load for instance an 'ordercredit', and then accessing an object of the ordercredit.

I use this code for getting the OrderCredit:

OrderCredit oc = CreditService.getOrderCredit(ordercredit.Id);

The code I use for loading is done using a DAO implementation:

[Transaction(TransactionPropagation.Required, ReadOnly = true)]
public OrderCredit GetOrderCredit(long ordercreditid)
{
    var creditrules = Session.CreateCriteria(typeof(OrderCredit));
    creditrules.Add(Restrictions.Eq("Id", ordercreditid));
    return creditrules.List<OrderCredit>()[0];
}

When I run this on my local machine, everything works fine, and I actually intended to load a list of those 'ordercredits', but that went wrong as well, so I tried a simpler step first.

The objects within the 'OrderCredit' are defined as [OneToMany].

When I put this on the testserver, and try to access the 'OrderObject' object of the loaded OrderCredit, I get the error:

NHibernate.LazyInitializationException: Initializing[.OrderObject#5496522]-Could not initialize proxy - no Session.

Code that fails:

Log.Debug(oc.OrderObject.Name);

Code that works:

Log.Debug(oc.Id);

This happens for any object that's part of the OrderCredit, but I am able to access the property fields of the OrderCredit (for instance the OrderCredit.Id).

Also, when I access any of the objects BEFORE I return the data to the original function calling the method, then it does cache the information or so, as I can access it then.

I've read a lot about this problem, like turning off Lazy, but that did not work for me either (or I did that on the wrong place).

The thing that frustrates me most, is the fact that it actually does work on my local machine, and not on the testserver. What could I be doing wrong?

Any help is highly appreciated.

1st update:

I am using now a GenericDao, using the default method of loading 1 ordercredit. I use the following code to load 1 ordercredit by Id.

OrderCredit oc = GenericService.Load<OrderCredit>(Id);

The code that's inside the GenericDAO is the following, BUT it does not end or breaks the session, which means I am able to access the objects attached to the ordercredit:

[Transaction(TransactionPropagation.Supports, ReadOnly = true)]
public T Load<T>(long id) where T : ISaveableObject
{
    var obj = Session.Load<T>(id);
    return obj;
}

This is nearly the same code as I had in the function which I included earlier in this question.

I'm now really confused because I don't know what it could be that ends the session. I will work with it now as it works, but I want to change it later on, so I can use my function to call the entire collection and access them via a for each loop.

Currently, I use my 'getOrderCredits' function to get the list of OrderCredit objects, and in the foreach, I get the Id, and use the GenericDao.Load to get the actual item, and can access the objects and such. Of course this is not the way it should be and needs to be.

I'd be amazed if I get this solved.

This is a common problem people have when using NHibernate. It happens because:

1. You open a session
2. You load an entity from the database which references another entity
3. You close the session
4. You try to access a property on your referenced entity
5. NHibernate tries to lazily load the entity from the database using the same session that loaded the parent entity
6. The session is closed, so NHibernate throws exceptions like woah.

You have a few options here:

1. Keep your session open longer, preferably using something like the unit of work pattern, which will give you tighter control.
2. Eagerly load your referenced entities when you query:

In your case as spring is managing your transaction for you the 2nd option is probably the quickest/easiest solution.

var creditrules = Session.CreateCriteria(typeof(OrderCredit));
creditrules.Add(Restrictions.Eq("Id", ordercreditid))
  .SetFetchMode("OrderObject", FetchMode.Eager);

This will load the OrderObject when you load the OrderCredit.