Implementa o contexto do nhibernate para armazenar a session, dentro do HttpContext, caso exista, ou dentro do CallContext

HybridSessionContext.cs

namespace Core.Data.NH
{
    using System.Runtime.Remoting.Messaging;
    using System.Web;
    using NHibernate;
    using NHibernate.Context;
    using NHibernate.Engine;

    /// <summary>
    /// Implementa o contexto do nhibernate para armazenar 
    /// a session, dentro do HttpContext, caso exista, ou 
    /// dentro do CallContext.
    /// </summary>
    public class HybridSessionContext : ICurrentSessionContext
    {
        /// <summary>
        /// Chave que armazena o valor.
        /// </summary>
        private const string SessionKey = "Core.Data.NH.HybridSessionContextKey";

        /// <summary>
        /// Session factory
        /// </summary>
        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1823:AvoidUnusedPrivateFields",
            Justification = "ICurrentSessionContext necessita de um construtor que receber sessionFactory.")]
        private readonly ISessionFactoryImplementor sessionFactory;

        /// <summary>
        /// Inicializa uma nova instância de SessionContext.
        /// </summary>
        /// <param name="sessionFactory">NHibernate session factory.</param>
        public HybridSessionContext(ISessionFactoryImplementor sessionFactory)
        {
            this.sessionFactory = sessionFactory;
        }

        /// <summary>
        /// Configura a session atual ao contexto.
        /// </summary>
        /// <param name="session">session</param>
        public static void Bind(ISession session)
        {
            var ctx = HttpContext.Current;
            if (ctx != null)
            {
                ctx.Items[SessionKey] = session;
            }
            else
            {
                CallContext.SetData(SessionKey, session);
            }
        }

        /// <summary>
        /// Retira a session do contexto.
        /// </summary>
        /// <returns>session</returns>
        public static ISession Unbind()
        {
            ISession session = null;

            var ctx = HttpContext.Current;
            if (ctx != null)
            {
                session = (ISession)ctx.Items[SessionKey];
                ctx.Items[SessionKey] = null;
            }
            else
            {
                session = (ISession)CallContext.GetData(SessionKey);
                CallContext.SetData(SessionKey, null);
            }

            return session;
        }

        /// <summary>
        /// Obtém a session atual.
        /// </summary>
        /// <returns>session atual</returns>
        public ISession CurrentSession()
        {
            ISession session = null;

            var ctx = HttpContext.Current;
            if (ctx != null)
            {
                session = (ISession)ctx.Items[SessionKey];
            }
            else
            {
                session = (ISession)CallContext.GetData(SessionKey);
            }

            return session;
        }
    }
}