public async void GetGroupTopicsAsync(string groupId, Dictionary<string, string> parameters = null)
        {
            if (groupTopicsFetchingQueue.Contains(groupId))
                return;

            groupTopicsFetchingQueue.Add(groupId);

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

            Dictionary<string, string> paramDict = new Dictionary<string, string>();
            paramDict["method"] = "flickr.groups.discuss.topics.getList";
            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["group_id"] = groupId;

            if (parameters != null)
            {
                foreach (var entry in parameters)
                {
                    paramDict[entry.Key] = entry.Value;
                }
            }

            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()))
            {
                groupTopicsFetchingQueue.Remove(groupId);

                GetGroupTopicsExceptionEventArgs exceptionEvt = null;

                if (response.StatusCode != HttpStatusCode.OK)
                {
                    HandleHTTPException(response);

                    exceptionEvt = new GetGroupTopicsExceptionEventArgs();
                    exceptionEvt.GroupId = groupId;
                    GroupTopicsException(this, exceptionEvt);
                    return;
                }

                string jsonString = await reader.ReadToEndAsync().ConfigureAwait(false);
                if (!TryHandleResponseException(jsonString, () => { GetGroupTopicsAsync(groupId, parameters); }))
                {
                    exceptionEvt = new GetGroupTopicsExceptionEventArgs();
                    exceptionEvt.GroupId = groupId;
                    GroupTopicsException(this, exceptionEvt);
                    return;
                }

                GetGroupTopicsEventArgs args = new GetGroupTopicsEventArgs();
                args.GroupId = groupId;
                args.Response = jsonString;
                GroupTopicsReturned.DispatchEvent(this, args);
            }
        }
        private void OnGroupTopicsReturned(object sender, GetGroupTopicsEventArgs e)
        {
            if (!Cinderella.CinderellaCore.GroupCache.ContainsKey(e.GroupId))
                return;

            FlickrGroup group = Cinderella.CinderellaCore.GroupCache[e.GroupId];

            JObject rawJson = JObject.Parse(e.Response);
            JObject rootJson = (JObject)rawJson["topics"];
            int TotalCount = int.Parse(rootJson["total"].ToString());
            int page = int.Parse(rootJson["page"].ToString());
            int numPages = int.Parse(rootJson["pages"].ToString());
            int perPage = int.Parse(rootJson["per_page"].ToString());

            List<Topic> newTopics = new List<Topic>();
            if (TotalCount > 0)
            {
                foreach (var entry in rootJson["topic"])
                {
                    JObject json = (JObject)entry;
                    Topic topic = TopicFactory.TopicWithJObject(json, group);

                    if (!group.Topics.Contains(topic))
                    {
                        group.Topics.Add(topic);
                        newTopics.Add(topic);
                    }
                }

            }

            // Dispatch event
            GroupTopicsUpdatedEventArgs evt = new GroupTopicsUpdatedEventArgs();
            evt.GroupId = group.ResourceId;
            evt.Page = page;
            evt.PageCount = numPages;
            evt.PerPage = perPage;
            evt.NewTopics = newTopics;
            GroupTopicsUpdated.DispatchEvent(this, evt);
        }