public async void GetEXIFAsync(string photoId)
        {
            if (IsGettingEXIFInfo(photoId))
                return;

            exifQueue.Add(photoId);

            string timestamp = DateTimeUtils.GetTimestamp();
            string nonce = Guid.NewGuid().ToString().Replace("-", null);

            Dictionary<string, string> paramDict = new Dictionary<string, string>();
            paramDict["method"] = "flickr.photos.getExif";
            paramDict["format"] = "json";
            paramDict["nojsoncallback"] = "1";
            paramDict["oauth_consumer_key"] = consumerKey;
            paramDict["oauth_nonce"] = nonce;
            paramDict["oauth_signature_method"] = "HMAC-SHA1";
            paramDict["oauth_timestamp"] = timestamp;
            paramDict["oauth_token"] = AccessToken;
            paramDict["oauth_version"] = "1.0";
            paramDict["photo_id"] = photoId;
            paramDict["extras"] = UrlHelper.Encode(commonExtraParameters);

            string paramString = GenerateParamString(paramDict);
            string signature = GenerateSignature("GET", AccessTokenSecret, "https://api.flickr.com/services/rest", paramString);
            string requestUrl = "https://api.flickr.com/services/rest?" + paramString + "&oauth_signature=" + signature;
            HttpWebResponse response = await DispatchRequest("GET", requestUrl, null).ConfigureAwait(false);
            using (StreamReader reader = new StreamReader(response.GetResponseStream()))
            {
                if(exifQueue.Contains(photoId))
                    exifQueue.Remove(photoId);

                GetEXIFExceptionEventArgs exceptionArgs = null;
                if (response.StatusCode != HttpStatusCode.OK)
                {
                    exceptionArgs = new GetEXIFExceptionEventArgs();
                    exceptionArgs.PhotoId = photoId;
                    EXIFException.DispatchEvent(this, exceptionArgs);

                    return;
                }

                string jsonString = await reader.ReadToEndAsync().ConfigureAwait(false);
                if (!IsResponseSuccess(jsonString))
                {
                    exceptionArgs = new GetEXIFExceptionEventArgs();
                    exceptionArgs.PhotoId = photoId;
                    EXIFException.DispatchEvent(this, exceptionArgs);

                    return;
                }


                GetEXIFEventArgs args = new GetEXIFEventArgs();
                args.PhotoId = photoId;
                args.Response = jsonString;
                EXIFReturned.DispatchEvent(this, args);
            }
        }
        private void OnEXIFException(object sender, GetEXIFExceptionEventArgs e)
        {
            Dispatcher.BeginInvoke(() =>
            {
                if (e.PhotoId != PhotoSource.ResourceId)
                    return;

                LoadingView.Visibility = Visibility.Collapsed;
                DescriptionLabel.Visibility = Visibility.Visible;
                DescriptionLabel.Text = AppResources.DetailPageLoadEXIFErrorText;
            });
        }