string result = "sms&stat=100&message=发送成功";

        string d = HttpUtility.ParseQueryString(result).Get("stat");

        string dd = HttpUtility.ParseQueryString(result).Get("message");

        string ddd = HttpUtility.ParseQueryString(result).Get("sms");

        NameValueCollection qscoll = HttpUtility.ParseQueryString(result);

        qscoll.Add("a", "nihao");

        string ss = qscoll.Get("a");

        string aaa = qscoll.ToString();

//aaa的结果sms&stat=100&message=%u53d1%u9001%u6210%u529f&a=nihao