Shows a simple implementation of using an OpenRasta Pipeline Contributor to manage nHibernate Sessions on a per request basis

NHibernateSessionPipelineContributor.cs

public class NHibernateSessionPipelineContributor : IPipelineContributor
    {
        private readonly IDependencyResolver _resolver;

        public NHibernateSessionPipelineContributor(IDependencyResolver resolver)
        {
            _resolver = resolver;
        }

        public void Initialize(IPipeline pipelineRunner)
        {
            pipelineRunner.Notify(StartSession)
                .After<KnownStages.IBegin>();

            pipelineRunner.Notify(FinishSession)
                .After<KnownStages.IOperationExecution>()
                .And
                .Before<KnownStages.IResponseCoding>();
        }
        private PipelineContinuation StartSession(ICommunicationContext arg)
        {
            var factory = _resolver.Resolve<ISessionFactory>();

            if (factory != null)
            {
                var sessionForRequest = factory.OpenSession();

                _resolver.AddDependencyInstance(typeof (ISession), sessionForRequest, DependencyLifetime.PerRequest);
            }

            return PipelineContinuation.Continue;
        }

        private PipelineContinuation FinishSession(ICommunicationContext arg)
        {
            var sessionForRequest = _resolver.Resolve<ISession>();

            if (sessionForRequest != null)
            {
                sessionForRequest.Dispose();
            }

            return PipelineContinuation.Continue;
        }

    }