尽管Service返回了一些数据，但HttpWebResponse仍返回null

Question

我的WCF REST服务正在返回数据合同列表。当我尝试读取响应时，我得到null，我注意到粗体代码中突出显示的下面的错误。 “length ='requestStream.Length'引发了'System.NotSupportedException'类型的异常”

        HttpWebResponse resp;
        try
        {
            if (httpMethod.ToUpper() == Constants.WEBHTTPGET)
            {
                if (request != null && request.ToString().Length > 0)
                    url += string.Format("/{0}", request.ToString());
            }

            // Create HttpWebRequest object 
            HttpWebRequest WebRequest = (HttpWebRequest)HttpWebRequest.Create(url);
            WebRequest.Method = httpMethod;
            WebRequest.ContentType = @"application/xml; charset=utf-8";

            if (IsTimeoutIncrementRequired(url))
                WebRequest.Timeout = (ConfigurationManager.AppSettings["WebRequestTimeout"] != null) ? (Convert.ToInt32(ConfigurationManager.AppSettings["WebRequestTimeout"], CultureInfo.InvariantCulture)) : Constants.WebRequestTimeout; 

            // Add HTTP headers 
            WebRequest.Headers.Add("x-ms-date", DateTime.UtcNow.ToString("R"));
            WebRequest.Headers.Add("x-ms-version", "2009-09-19");


            ServicePointManager.ServerCertificateValidationCallback += new RemoteCertificateValidationCallback(ValidateRemoteCertificate);
            if (HttpContext.Current.Session["CurrentUser"] != null)
            {
                DataContract.User userObj = (DataContract.User)HttpContext.Current.Session["CurrentUser"];
                //Set Header content type and Authetincation
                WebRequest.Headers.Add("Authorization", GetAuthHeader(userObj.UserName, userObj.Password));
                CultureInfo culture = ResolveCulture();
                if (culture != null && culture.Name != null)
                {
                    WebRequest.Headers.Add("ClientBrowserCulture", culture.Name);
                }
                else
                {
                    WebRequest.Headers.Add("ClientBrowserCulture", System.Configuration.ConfigurationManager.AppSettings["DISCurrentCulture"]);
                }

            }
            if (httpMethod.ToUpper() == Constants.WEBHTTPPOST)
            {
                string xmlString = ObjectToXml(request);
                WebRequest.ContentLength = Encoding.UTF8.GetByteCount(xmlString);
                **using (Stream stream = WebRequest.GetRequestStream())
                {
                    stream.Write(Encoding.UTF8.GetBytes(xmlString), 0, Encoding.UTF8.GetByteCount(xmlString));
                }**
            }
            else
            {
                WebRequest.ContentLength = 0;
            }

            resp = WebRequest.GetResponse() as HttpWebResponse;


        }