private void GetSearchResponse(HttpWebRequest httpWebRequest)
            {
                try
                {
                    using (var httpWebResponse = httpWebRequest.GetResponse() as HttpWebResponse)
                    {
                        using (var stream = httpWebResponse.GetResponseStream())
                        {
                            ProcessSearchResponse(stream);
                        }
                    }
                }
                catch (WebException ex)
                {//catch and log the error
                    }



     stack trace : "{"error":{"code":"-2147024891,
        System.UnauthorizedAccessException","message":{"lang":"en-US","value":"Access
     denied. You do not have permission to perform this action or access
    this resource."}}}"

[MessageSecurityException: The HTTP request is unauthorized with client authentication scheme 'Anonymous'. The authentication header received from the server was ''.]

request.Headers["X-RequestDigest"] = formDigestValue;