//GET LOCATIONS BY LOCATION PREFIX, LIBRARY, USERID
        public JsonResult GetLocationsByPrefix(int id, string prefix)
        {
            List <SelectListItem> LocByPrefix = new List <SelectListItem>();

            LocByPrefix.Add(new SelectListItem {
                Text = "Tất cả", Value = ""
            });

            foreach (var lbp in db.FPT_CIR_GET_LOCFULLNAME_LIBUSER_SEL((int)Session["UserID"], id, prefix))
            {
                LocByPrefix.Add(new SelectListItem {
                    Text = lbp.Symbol, Value = lbp.ID.ToString()
                });
            }
            if (id == 81)
            {
                foreach (var lbp in db.FPT_CIR_GET_LOCFULLNAME_LIBUSER_SEL((int)Session["UserID"], 20, prefix))
                {
                    if (lbp.ID == 13 || lbp.ID == 15 || lbp.ID == 16 || lbp.ID == 27)
                    {
                        LocByPrefix.Add(new SelectListItem {
                            Text = lbp.Symbol, Value = lbp.ID.ToString()
                        });
                    }
                }
                if (prefix.Equals("TK/"))
                {
                    foreach (var lbp in db.FPT_CIR_GET_LOCFULLNAME_LIBUSER_SEL((int)Session["UserID"], id, "LV/"))
                    {
                        LocByPrefix.Add(new SelectListItem {
                            Text = lbp.Symbol, Value = lbp.ID.ToString()
                        });
                    }
                }
            }

            return(Json(new SelectList(LocByPrefix, "Value", "Text")));
        }