C# 参数按照ASCII码从小到大排序（字典序）

在对接第三方支付的时候，第三方会要求参数按照ASCII码从小到大排序。如下：

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;
}