var room = rooms.FirstOrDefault(r => r.Value.Users.FirstOrDefault(u => u.Id == Context.UserIdentifier) != null);
            var user = room.Value.Users.FirstOrDefault(u => u.Id == Context.UserIdentifier);
            if (user != null)
                room.Value.Users.Remove(user);
            Clients.Group(room.Key).UserLeft(Context.UserIdentifier);
            if(room.Value.Users.Count == 0)
            {
                Clients.All.RoomAbandoned(room.Key);
                rooms.Remove(room.Key);
            }
            return base.OnDisconnectedAsync(exception);