// POST api/PruebaRoles
        public HttpResponseMessage Posttb_roles(tb_roles tb_roles)
        {
            if (ModelState.IsValid)
            {
                db.tb_roles.Add(tb_roles);
                db.SaveChanges();

                HttpResponseMessage response = Request.CreateResponse(HttpStatusCode.Created, tb_roles);
                response.Headers.Location = new Uri(Url.Link("DefaultApi", new { id = tb_roles.id_rol }));
                return response;
            }
            else
            {
                return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ModelState);
            }
        }
        public HttpResponseMessage UpdateRol(long id, tb_roles tb_roles)
        {
            if (!ModelState.IsValid)
            {
                return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ModelState);
            }

            if (id != tb_roles.id_rol)
            {
                return Request.CreateResponse(HttpStatusCode.BadRequest);
            }

            db.Entry(tb_roles).State = System.Data.EntityState.Modified;

            try
            {
                db.SaveChanges();
            }
            catch (DbUpdateConcurrencyException ex)
            {
                return Request.CreateErrorResponse(HttpStatusCode.NotFound, ex);
            }

            return Request.CreateResponse(HttpStatusCode.OK);
        }