What is the best way to solve a coupling problem involving Log features?

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C#

OOP

logging

I'm doing an asp.net system using nHibernate for persistence.
In my code I'm separating the business classes/objects from repository. I have a set of repository classes with internally use nhibernate, but this is transparent to my application.
I have a need to log every CRUD operation in my repository, so I created a log class and a log repository, but all repositories need to have two things in order to work properly with the log:
1) An instance of the user class, to register who is the user that perfomed the crud operation
2) An instance of the HTTPContext object, to get some information about session, server and browser.

I know it is the wrong way to do this, but I dont know the best way. If I put log logic in the base repository class I have the repository coupled with HTTPSession and can't use my business objects in a windows form application.
If I do log logic outside repository I need to do this in the application layer, and maybe replicate log-related code throgh my application.

Besides, how can I "inject" the user and session information in my repository class? I am doing this on the constructor.

Below follows an example of my code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using LiderTel.Modelo;

namespace LiderTel.Persistencia
{
    public class BaseRepositorio<T> where T: Entity
    {
        private Sessao _sessaoInjetadaRepositorio;
        private Usuario _usuarIoinjetadoRepositorio;

        protected virtual Sessao GetSession()
        {
            return _sessaoInjetadaRepositorio;
        }

        protected virtual Usuario GetUser()
        {
            return _usuarIoinjetadoRepositorio;
        }

        public BaseRepositorio(Sessao sess, Usuario usu)
        {
            _sessaoInjetadaRepositorio = sess;
            _usuarIoinjetadoRepositorio = usu;
        }

        public BaseRepositorio(Sessao sess)
            : this(sess, sess==null?null:sess.UsuarioCriador)
        {

        }

        public BaseRepositorio()
            : this(SessionServices.GetSessaoCorrente(),  SessionServices.GetSessaoCorrente()==null?null:SessionServices.GetSessaoCorrente().UsuarioCriador)
        {

        }


        private string GetUserID()
        {
            return (GetUser() != null) ? GetUser().ID.ToString() : "";
        }

        public virtual void Add(T ent)
        {
            ent.Criacao = DateTime.Now;
            ent.UsuarioCriador = GetUser();
            ent.Excluido = false;
            ent.Ativo = true;
            NHibernateHelper.GetDefaultSession().Save(ent);



            Log log = new Log();
            log.Acao = string.Format("{0} {1} created by {2}.", ent.GetType().Name, ent.ID.ToString(), GetUserID());
            log.TipoEvento = TipoEventoLog.Inclusao;
            log.Entidade = ent.ID;
            if (GetSession() != null)
            {
                log.SessaoID = GetSession().ID;
            }
            log.ComoEstava = ent.InternalToString();

            LogRepository logrep = new LogRepository(GetSession(), GetUser());
            logrep.Add(log);
        }
    }
}

sorry about my english