public void NavigateTo(int id)
{
if (CurrentItem != null)
{
History.Push(CurrentItem.Id);
}
CurrentItem = AllItems.SingleOrDefault(i => i.Id == id);
if (CurrentItem != null)
{
grdChildren.ItemsSource = JArray.Parse(CurrentItem.ChildrenOrder).Values <int>().Select(ch => AllItems.SingleOrDefault(i => i.Id == ch));
}
btnBack.IsEnabled = History.Count > 0;
}