NHibernate开源框架Cuyahoga学习之数据访问泛型约束的实现

//泛型约束接口
using System;
using System.Collections.Generic;
using Cuyahoga.Core.Domain;
using NHibernate.Criterion;
namespace Cuyahoga.Core.DataAccess
{
    public interface IContentItemDao<T> where T : IContentItem
    {
        T GetById(long id);
        T GetById(Guid id);
        IList<T> GetAll();
        IList<T> GetBySite(Site site);
        T Save(T entity);
        void Delete(T entity);
    }
}
//接口实现
using System;
using System.Collections.Generic;
using Cuyahoga.Core.Domain;
using NHibernate;
using NHibernate.Criterion;
using Castle.Facilities.NHibernateIntegration;
using Castle.Services.Transaction;
namespace Cuyahoga.Core.DataAccess
{
    [Transactional]
    public class ContentItemDao<T> : IContentItemDao<T> where T : IContentItem
    {
        protected readonly ISessionManager SessionManager;
        protected readonly Type PersistentType = typeof(T);
        public ContentItemDao(ISessionManager sessionManager)
        {
            this.SessionManager = sessionManager;
        }
        protected ISession GetSession()
        {
            return this.SessionManager.OpenSession();
        }
        public T GetById(long id)
        {
            return this.GetSession().Get<T>(id);
        }
        public T GetById(Guid id)
        {
            return this.GetSession().Get<T>(id);    
}
        public IList<T> GetAll()
        {
            ICriteria criteria = this.GetSession().CreateCriteria(PersistentType);
            return criteria.List<T>();
        }
        public IList<T> GetBySite(Site site)
        {
            ICriteria criteria = this.GetSession().CreateCriteria(PersistentType)
                .CreateCriteria("Section", "s")
                    .Add(Expression.Eq("Site", site));
            return criteria.List<T>();
        }
        [Transaction(TransactionMode.Requires)]
        public T Save(T entity)
        {
            this.GetSession().SaveOrUpdate(entity);
            return entity;
        }
        [Transaction(TransactionMode.Requires)]
        public void Delete(T entity)
        {
            this.GetSession().Delete(entity);
        }
    }
}