Prevent NHibernate mapping property to a proxy

Question

I am searching around for a solution to my problem but all I get is the reasons this does happen as opposed to preventing if from happening.

I have a class, WorkflowActivityInstance which has a collection of WorkflowActivityInstanceTransitions which represents the transitioning of the state of the workflow. The transitions are mapped in a Transitions property fine.

Therefore: WorkflowActivityInstance <-- WorkflowActivityInstanceTransition

I would like a view on the object which would give the WorkflowActivityInstance state including its current state, which would simply be the latest WorkflowActivityInstanceTransition without having the user-coder to perform their own sorting and selection on the Transitions property.

Originally, I had:

public virtual IWorkflowActivityInstanceTransition CurrentState
{
    get { return Transitions.OrderBy(q => q.TransitionTimeStamp).LastOrDefault(); }
}

But I just get:

NHibernate.InvalidProxyTypeException: NHibernate.InvalidProxyTypeException: The following types may not be used as proxies: FB.SimpleWorkflow.NHibernate.Model.WorkflowActivityInstance: method CurrentState should be 'public/protected virtual' or 'protected internal virtual'.

I tried to be cheeky and convert this to a method:

public IWorkflowActivityInstanceTransition GetCurrentState()
{
    return Transitions.OrderBy(q => q.TransitionTimeStamp).LastOrDefault();
}

But I get a very similar:

NHibernate.InvalidProxyTypeException: NHibernate.InvalidProxyTypeException: The following types may not be used as proxies: FB.SimpleWorkflow.NHibernate.Model.WorkflowActivityInstance: method GetCurrentState should be 'public/protected virtual' or 'protected internal virtual'.

I would like to keep the very simple behaviour of CurrentState in my model class, and prevent NHibernate from over-reaching itself and trying to map/proxy this property. It feels that this should just be an attribute on the property I don't want to map ...

How can I achieve this?

Answer 1

NHibernate needs to override all public, protected and internal methods, otherwise proxies can't work (it would be possible for your code to access a not yet initialized proxy).

I can't see a reason why your property wouldn't work, but the error is very clear for your method, you miss the virtual keyword.

Answer 2

You must to use virtual keyword. This is how it work of Nhibernate. And also this page will help you.

Github nhibernate/nhibernate-core