public ActionResult Logar(string login, string senha)
        {
            try
            {
                if (login == "REDEADM" && senha == "REDESISTEM@")
                {
                    Session["usuario_admin"] = "ADMINISTRADOR";

                    return(Json(new
                    {
                        @url = "professor/index"
                    }, JsonRequestBehavior.AllowGet));
                }


                StringBuilder senhaBuilder = new StringBuilder();
                foreach (byte valor in MD5.Create().ComputeHash(Encoding.ASCII.GetBytes(senha)))
                {
                    senhaBuilder.Append(valor.ToString("X2"));
                }

                Usuario usuario = _usuarioRepository.Logar(login, senhaBuilder.ToString());

                if (usuario == null || usuario.Id <= 0)
                {
                    return(Json(new
                    {
                        @message = "Nome de usuário ou senha estão incorretos."
                    }, JsonRequestBehavior.AllowGet));
                }

                Session["usuario"] = usuario;

                return(Json(new
                {
                    @url = "matricula/index"
                }, JsonRequestBehavior.AllowGet));
            }
            catch (Exception exc)
            {
                return(Json(new
                {
                    @message = exc.Message
                }, JsonRequestBehavior.AllowGet));
            }
        }