How can we handle ISessionFactory in NHibernate with NUnitOfWork

Hibernate ORM
1

class NUnitOfWork : INUnitofWork
{
private NHibernate.ISessionFactory sessionFactory;

    private NHibernate.ISession session;
    public NHibernate.ISession Session { get { return this.session; } }

    private NHibernate.ITransaction transaction;
    private static IInternalLogger logger;
    private ILogProvider logProvider;

    public NUnitOfWork(NHibernate.ISessionFactory sessionFactory, ILogProvider logProvider)
    {
        this.sessionFactory = sessionFactory;
        this.logProvider = logProvider;
        logger = logProvider.LoggerFor(typeof(NUnitOfWork));
        logger.Debug("Logger acquired successfully.");
    }

    public void Open()
    {
        logger.Debug("Open() invoked.");
        if (null == this.sessionFactory)
            throw new ArgumentNullException("ISessionFactory instance must be available.");
        logger.Debug("Trying to acquire ISession instance from ISessionFactory instance.");
        this.session = this.sessionFactory.OpenSession();
        logger.Info("Acquired ISession instance.");
        if (null == this.transaction)
        {
            logger.Debug("Trying to begin the transaction.");
            this.transaction = session.BeginTransaction();
            logger.Info("Transaction begun successfully.");
        }
        else if (null != this.transaction)
        {               
            if (!this.transaction.IsActive)
            {
                logger.Debug("The current transaction isn't active.");
                this.transaction.Begin();
                logger.Info("The current transaction is set to active mode now.");
            }                
        }
        else
            throw new ApplicationException("The current transaction is active.");
    }

    public void Commit()
    {
        logger.Debug("Commit() invoked.");
        if (null == this.transaction)
            throw new ApplicationException("Transaction needs to be open before a calling the commit method.");
        this.transaction.Commit();
        this.transaction.Dispose();
        this.transaction = null;
    }

    public void Rollback()
    {
        logger.Debug("Rollback invoked.");
        if (null == this.transaction)
            throw new ApplicationException("Transaction needs to be open before a calling the Rollback method.");
        this.transaction.Rollback();
    }

    public void Close()
    {
        logger.Debug("Close() invoked.");
        if (null != this.transaction)
        {
            logger.Debug("Trying to terminate transaction.");
            this.transaction.Dispose();
            logger.Debug("Transaction disposed successfully.");
        }
        this.transaction = null;
        if (null != this.sessionFactory)
        {
            if (!this.sessionFactory.IsClosed)
            {
                if (null != this.Session)
                {
                    if (this.Session.IsOpen)
                    {
                        try
                        {
                            logger.Debug("Trying to close the session.");
                            this.Session.Close();
                            logger.Info("Session closed successfully.");
                        }
                        catch (Exception ex)
                        {
                            logger.Warn("Unable to close the session.", ex);
                        }
                    }
                }
                logger.Debug("Trying to close ISessionFactory instance.");
                this.sessionFactory.Close();
                logger.Info("ISessionFactory closed successfully.");
            }
            else
                logger.Debug("ISessionFactory instance is already in a closed state.");

        }
    }

    public void Dispose()
    {

        logger.Debug("Dispose() invoked.");
        this.Close();           

    }

}

using this code getting error like
Session is closed! Object name: ‘ISession’.
ObjectDisposedException
There is already an open DataReader associated with this Command which must be closed first.