webserver获取信息

protected void btnSubmit_Click(object sender, EventArgs e)
        {
            string strReqXML = "<?xml version=\"1.0\" encoding=\"utf-8\"?><soap:Envelope xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\" xmlns:soap=\"http://schemas.xmlsoap.org/soap/envelope/\"><soap:Body><getWeatherbyCityName xmlns=\"http://WebXml.com.cn/\"><theCityName>" + txtCity.Text + "</theCityName></getWeatherbyCityName></soap:Body></soap:Envelope>";//getWeatherbyCityName方法，theCityName参数名
            byte[] buff = System.Text.Encoding.UTF8.GetBytes(strReqXML);
            HttpWebRequest hwr = (HttpWebRequest)HttpWebRequest.Create("http://www.webxml.com.cn/WebServices/WeatherWebService.asmx");
            hwr.ContentType = "text/xml; charset=utf-8";
            hwr.ContentLength = buff.Length;
            hwr.Method = "POST";
            Stream sr = hwr.GetRequestStream();
            sr.Write(buff, 0, buff.Length);
            WebResponse wr = hwr.GetResponse();
            DataSet ds = new DataSet();
            ds.ReadXml(wr.GetResponseStream());
            txtResult.Text = ds.Tables[3].Rows[1][0].ToString();//就能在返回的数据集中获取信息
            wr.Close();
            sr.Close();
        }