Object Relational Mapping (ORM) using NHibernate - Part 7 of 8 Completing the Ecommerce Example

using System;
using NHibernate;
using NHibernate.Cfg;
using NHibernate.Tool.hbm2ddl;

namespace ECommerceSystem.Repository
{
    public interface IRepository<T>
    {
        void addItem(T item);

        void removeItem(T item);

        void updateItem(T item);

        T getItemById(long item_id);

        int  getItemCount();


    }

    internal class NHibernateHelper
    {
        private NHibernateHelper()
        {
            Configuration cfg = new Configuration();
            cfg.Configure();
            sessionFactory = cfg.BuildSessionFactory();
            new SchemaExport(cfg).Execute(false, true, false); 
        }

        public static NHibernateHelper Create()
        {
            if (nHibHelper == null)
            {

                try
                {
                    nHibHelper = new NHibernateHelper();
                }
                catch (Exception ex)
                {
                    nHibHelper = null;
                }
            }

            return nHibHelper;
        }
        public ISession Session
        {
            get { return sessionFactory.OpenSession(); }
        }
        ISessionFactory sessionFactory;
        static NHibernateHelper nHibHelper;
    }
}