static void

using System;
using System.Collections.Generic;
using NHibernate;
 
namespace Northwind
{
    /// <summary>
    /// A generic repository. Normally this would be a base class of customized entity repositories- not directly exposed.
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <remarks>
    /// All operations are wrapped with <see cref="TransactionRequired"/>. If there is NO open transaction, they open a transaction and commit immediately. If there is an open transaction, nothing is commited, so you should commit at a higher level.
    /// </remarks>
    public class GenericRepository<T> where T : new()
    {
        protected ISession Session
        {
            get { return SessionManager.Instance.Session; }
        }
 
        #region Read
        /// <summary>
        /// Loads the specified id. Throws an exception if not in database.
        /// </summary>
        public T Load(object id)
        {
            using (TransactionRequired transaction = new TransactionRequired())
            {
                return Session.Load<T>(id);
            }
        }
 
        /// <summary>
        /// Gets the Id. Returns null if there is no matching row
        /// </summary>
        public T GetById(object id)
        {
            using (TransactionRequired transaction = new TransactionRequired())
            {
                return Session.Get<T>(id);
            }
        }
 
        /// <summary>
        /// Finds all records. Consider <see cref="FindPage"/> for large result sets.
        /// </summary>
        public ICollection<T> FindAll()
        {
            using (TransactionRequired transaction = new TransactionRequired())
            {
                return Session.CreateCriteria(typeof(T)).List<T>();
            }
        }
 
        /// <summary>
        /// Counts the number of records.
        /// </summary>
        public int Count()
        {
            ICriteria criteria = Session.CreateCriteria(typeof(T));
            using (TransactionRequired transaction = new TransactionRequired())
            {
                return criteria.SetProjection(NHibernate.Criterion.Projections.RowCount()).UniqueResult<int>();
            }
        }
 
        /// <summary>
        /// Finds records by page.
        /// </summary>
        /// <param name="pageStartRow">The page start row.</param>
        /// <param name="pageSize">Size of the page.</param>
        public IList<T> FindPage(int pageStartRow, int pageSize)
        {
            ICriteria criteria = Session.CreateCriteria(typeof(T));
            criteria.SetFirstResult(pageStartRow);
            criteria.SetMaxResults(pageSize);
            using (TransactionRequired transaction = new TransactionRequired())
            {
                return criteria.List<T>();
            }
        }
 
        /// <summary>
        /// Finds records by page, sorted.
        /// </summary>
        public IList<T> FindSortedPage(int pageStartRow, int pageSize, string sortBy, bool descending)
        {
            ICriteria criteria = Session.CreateCriteria(typeof(T));
 
            if (descending)
                criteria.AddOrder(NHibernate.Criterion.Order.Desc(sortBy));
            else
                criteria.AddOrder(NHibernate.Criterion.Order.Asc(sortBy));
 
            criteria.SetFirstResult(pageStartRow);
            criteria.SetMaxResults(pageSize);
            using (TransactionRequired transaction = new TransactionRequired())
            {
                return criteria.List<T>();
            }
        }
        #endregion
 
        #region Update
        /// <summary>
        /// Saves the specified object within a transaction.
        /// </summary>
        public void Save(T entity)
        {
            using (TransactionRequired transaction = new TransactionRequired())
            {
                Session.Save(entity);
                transaction.Commit(); //flush to database
            }
        }
 
        /// <summary>
        /// Saves the specified object within a transaction.
        /// </summary>
        public void SaveOrUpdate(T entity)
        {
            using (TransactionRequired transaction = new TransactionRequired())
            {
                Session.SaveOrUpdate(entity);
                transaction.Commit(); //flush to database
            }
        }
 
        /// <summary>
        /// Deletes the specified object within a transaction.
        /// </summary>
        public void Delete(T entity)
        {
            using (TransactionRequired transaction = new TransactionRequired())
            {
                Session.Delete(entity);
                transaction.Commit(); //flush to database
            }
        }
        #endregion
    }
}