private void OnUserActivityChanged(User user) { _synchronizationContext.InvokeIfRequired(() => { foreach (var room in this.rooms) { UserViewModel userVm = room.Users.FirstOrDefault(u => u.Name == user.Name); if (userVm != null) { if (userVm.Status != user.Status) { userVm.Status = user.Status; // room.AddNotification(String.Format("{0} has become {1}.", user.Name, userVm.Status)); } } } }); }