C parameters are sorted from small to large according to ASCII code (lexicographic order)

When paying for the third party, the third party will require the parameters to be sorted from small to large according to ASCII code. As follows:

public static void requestPay()
 {  Dictionary<string, string> dics = new Dictionary<string, string>();
  dics.Add("amount", amount);
  dics.Add("callback_url", callback_url);
  dics.Add("goodsname", goodsname);
  dics.Add("merchno", merchno);
  dics.Add("notify_url", notify_url);
  dics.Add("ordno", ordno);
  dics.Add("organno", organno);
  dics.Add("version", version);
  dics.Add("paytype", paytype);
  getParamSrc(dics);
}

public static String getParamSrc(Dictionary<string, string> paramsMap)
{
  var vDic = (from objDic in paramsMap orderby objDic.Key ascending select objDic);
  StringBuilder str = new StringBuilder();
  foreach (KeyValuePair<string, string> kv in vDic)
  {
   string pkey = kv.Key;
   string pvalue = kv.Value;
   str.Append(pkey + "=" + pvalue + "&");
  }
  String result = str.ToString().Substring(0, str.ToString().Length - 1);
  return result;
}