SignalR.DefaultSubscription.DefaultSubscription C# (CSharp) Method

        public DefaultSubscription(string identity,
                                   IEnumerable<string> eventKeys,
                                   IDictionary<string, Topic> topics,
                                   string cursor,
                                   Func<MessageResult, Task<bool>> callback,
                                   int maxMessages,
                                   IPerformanceCounterWriter counters)
            : base(identity, eventKeys, callback, maxMessages, counters)
        {
            IEnumerable<Cursor> cursors = null;
            if (cursor == null)
            {
                cursors = from key in eventKeys
                          select new Cursor
                          {
                              Key = key,
                              Id = GetMessageId(topics, key)
                          };
            }
            else
            {
               cursors = Cursor.GetCursors(cursor);
            }

            _cursors = new List<Cursor>(cursors);
            _cursorTopics = new List<Topic>();

            if (!String.IsNullOrEmpty(cursor))
            {
                // Update all of the cursors so we're within the range
                for (int i = _cursors.Count - 1; i >= 0; i--)
                {
                    Cursor c = _cursors[i];
                    Topic topic;
                    if (!eventKeys.Contains(c.Key))
                    {
                        _cursors.Remove(c);
                    }
                    else if (topics.TryGetValue(_cursors[i].Key, out topic) && _cursors[i].Id > topic.Store.GetMessageCount())
                    {
                        UpdateCursor(c.Key, 0);
                    }
                }
            }

            // Add dummy entries so they can be filled in
            for (int i = 0; i < _cursors.Count; i++)
            {
                _cursorTopics.Add(null);
            }
        }