正则表达式-验证是否是6位数字

Regex regex = new Regex(@"^\d{6}$", RegexOptions.ECMAScript);
            while (true)
            {
                Console.WriteLine("请输入一个字符串");
                string postcode = Console.ReadLine();
                bool b = regex.IsMatch(postcode);
                Console.WriteLine(b);
            }