public ActionResult TablesJson(string dbName, string connectionStringName = "SqlServerHelper")
        {
            IEnumerable <TablesView> list_tables = null;
            string connectionString = ConnectionString.connectionString(connectionStringName);

            if (!string.IsNullOrWhiteSpace(connectionString))
            {
                list_tables = CacheHelper.GetCache(connectionString + "_Table_" + dbName) as IEnumerable <TablesView>;
                if (list_tables == null || list_tables.Count() <= 0)
                {
                    list_tables = homeDA.GetTables(dbName, connectionStringName);
                    CacheHelper.SetCache(connectionString + "_Table_" + dbName, list_tables, TimeSpan.FromHours(2));
                }
            }
            return(Json(list_tables, "text/plain", JsonRequestBehavior.AllowGet));
        }