使用XML post方法调用Web服务并以XML格式获取响应，这是非常慢的响应

Question

这里我得到了正确的结果，但我的问题是来自服务器的响应很慢。 请建议任何其他最快的方法来调用Web服务。帮助赞赏。

 String xml = "<?xml version=\"1.0\" encoding=\"utf-8\" ?><availabilityRequest cancelpolicy = \"Y\">with more condition</availabilityRequest>


String responseStr = postXMLData("http://service-url", xml);
                    XmlDocument doc = new XmlDocument();
                    doc.LoadXml(responseStr);

public String postXMLData(string destinationUrl, string requestXml)
    {
        string responseStr = "";
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(destinationUrl);
        byte[] bytes;
        bytes = System.Text.Encoding.ASCII.GetBytes(requestXml);
        request.ContentType = "text/xml; encoding='utf-8'";
        request.ContentLength = bytes.Length;
        request.Method = "POST";
        Stream requestStream = request.GetRequestStream();
        requestStream.Write(bytes, 0, bytes.Length);
        requestStream.Close();
        HttpWebResponse response;
        response = (HttpWebResponse)request.GetResponse();
        if (response.StatusCode == HttpStatusCode.OK)
        {
            Stream responseStream = response.GetResponseStream();
            responseStr = new StreamReader(responseStream).ReadToEnd().Trim();
        }
        return responseStr;
    }