http请求soap

public static string GetSOAPReSource(string url, string datastr)
        {

            //发起请求
            Uri uri = new Uri(url);
            WebRequest webRequest = WebRequest.Create(uri);
            webRequest.ContentType = "text/xml; charset=utf-8";
            webRequest.Method = "POST";
            using (Stream requestStream = webRequest.GetRequestStream())
            {
                byte[] paramBytes = Encoding.UTF8.GetBytes(datastr.ToString());
                requestStream.Write(paramBytes, 0, paramBytes.Length);
            }

            //响应
            WebResponse webResponse = webRequest.GetResponse();
            using (StreamReader myStreamReader = new StreamReader(webResponse.GetResponseStream(), Encoding.UTF8))
            {
                string result = "";
                return result = myStreamReader.ReadToEnd();
            }
        }