public override void OnDeactivated()
{
base.OnDeactivated(); // CollectionModuleBase handles deactivation of common parts
ShelvesList.Deactivate();
BookDetails.Deactivate();
selected_shelves = null;
current_book_disposable.Dispose();
current_book_disposable = null;
SearchField.Clear(); // This will also clear the search_results
Books = null;
book_view_models.DisposeAll();
book_view_models = null;
}