关于访问链接返回XML的获取数据

1. 返回DataSet格式;

        /// <summary>
        /// 向某个url提交数据并读取该地址返回的xml,并将xml转换成dataset,并返回dataset中某个表
        /// </summary>
        /// <param name="url">提交的低至</param>
        /// <param name="param">参数</param>
        /// <param name="tableName">表名</param>
        /// <param name="encoding">编码格式</param>
        /// <returns></returns>
        public static DataSet PostData(string url, string param, String tableName, Encoding encoding)
        {
           #region post数据
            DataSet ds = new DataSet(); DataTable dt = new DataTable();
            HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);
            req.Timeout = 120000;
            try
            {
                byte[] requestbytes = encoding.GetBytes(param);
                req.Method = "post";
                req.ContentType = "application/x-www-form-urlencoded";
                req.ContentLength = requestbytes.Length;
                System.IO.Stream requeststream = req.GetRequestStream();
                requeststream.Write(requestbytes, 0, requestbytes.Length);
                requeststream.Close();
                HttpWebResponse res = (HttpWebResponse)req.GetResponse();
                System.IO.StreamReader sr = new System.IO.StreamReader(res.GetResponseStream(), encoding);
                String backstr = sr.ReadToEnd();
                StringReader txtReader = new StringReader(backstr);
                XmlTextReader xmlReader = new XmlTextReader(txtReader);
                ds.ReadXml(xmlReader);
                sr.Close();
                res.Close();
                sr.Dispose();
            }
            catch
            {
                return null;
            }
            //条件判断
            //if (ds != null && ds.Tables.Count > 0 && ds.Tables[tableName] != null)
            //{
            //    dt = ds.Tables[tableName].Copy();
            //}
            if (ds != null && ds.Tables.Count > 0)
            {
                //  dt = ds.Tables[tableName].Copy();
                return ds;
            }
            return ds;
            #endregion
        }

2. 返回字符串

                string url = Config.PassportUserInfoUrl + "&userid=" + userid;//可以把链接放到配置文件中
                string result = SlRequest.GetResponse(url, "");
                XmlDocument doc = new XmlDocument();
                doc.LoadXml(result);
                XmlNode node = doc.SelectSingleNode("soufun_passport/common");//选择XML节点的值
                if (node != null)
                {
                    string resMsg = node.SelectSingleNode("return_result").InnerText;
                    if (resMsg == "100")
                    {
                       //此处可以定义一个User实体类, 来接收关于User的Inforeturn user;
                    }
                    else
                    {
                        errorMessage = node.SelectSingleNode("error_reason").InnerText;
                        return null;
                    } 
                //此处讲判断某个XML节点下面有几个子节点

                   if (node.ChildNodes.Count > 3)
                   {
                        resMsg = "";
                    }

 注: C#将XMLDocument转化为String函数

       /// 将XmlDocument转化为string  
       /// </summary>  
       /// <param name="xmlDoc"></param>  
       /// <returns></returns>  
       public string ConvertXmlToString(XmlDocument xmlDoc)  
       {  
           MemoryStream stream = new MemoryStream();  
           XmlTextWriter writer = new XmlTextWriter(stream, null);  
           writer.Formatting = Formatting.Indented;  
           xmlDoc.Save(writer);   
    StreamReader sr = new StreamReader(stream, System.Text.Encoding.UTF8);  
           stream.Position = 0;  
           string xmlString = sr.ReadToEnd();  
           sr.Close();  
           stream.Close();   
    return xmlString;  
       }