private void Feedback_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
if ((e.OldItems == null || e.OldItems.Count == 0) && e.NewItems != null && e.NewItems.Count > 0)
{
e.NewItems.OfType <Feedback>().Where(f => !f.IsPermanent).ForEach(f => InitializeTimer(f));
}
HasFeedback = Feedback.Any();
}