/// <summary>
        ///     no caching
        /// </summary>
        /// <param name="tableName"></param>
        /// <param name="type"></param>
        /// <param name="columns"></param>
        /// <param name="sql"></param>
        /// <returns></returns>
        public static DataTable GetTable(string tableName, AppVar.ConnectionStringType type, string[] columns = null,
                                         string sql = null)
        {
            var connectionString = AppVar.GetConnectionString(type);

            return(GetTable(tableName, connectionString, columns, sql));
        }