获取XML里指定的节点内容信息

    HttpContent bw = new StringContent(StrXml, Encoding.UTF8, "application/Xml");
                var Msg = await _httpClientFactory.CreateClient().PostAsync("http://xxxxx/api/kpbusiness", bw);
                var ss = Msg.Content.ReadAsStringAsync();
                StringReader Reader = new StringReader(ss.Result);
                XmlDocument xmlDoc = new XmlDocument();
                xmlDoc.Load(Reader);
                XmlNodeList topM = xmlDoc.SelectNodes("//business");
                string returncode;
                string returnmsg;
                string retappid;
                string retid;
                foreach (XmlElement element in topM)
                {
                     returncode = element.GetElementsByTagName("returncode")[0].InnerText;
                     returnmsg = element.GetElementsByTagName("returnmsg")[0].InnerText;
                     retappid = element.GetElementsByTagName("returncode")[0].InnerText;
                     retid = element.GetElementsByTagName("returncode")[0].InnerText;
                }