Catrobat.IDE.WindowsPhone.Controls.FormulaControls.FormulaViewer.TokensPropertyChanged C# (CSharp) Метод

        private void TokensPropertyChanged(DependencyPropertyChangedEventArgs e)
        {
            var oldValue = (ObservableCollection<IFormulaToken>) e.OldValue;
            var newValue = (ObservableCollection<IFormulaToken>) e.NewValue;

            InitContainers();

            if (oldValue != null) oldValue.CollectionChanged -= Tokens_CollectionChanged;
            if (newValue != null) newValue.CollectionChanged += Tokens_CollectionChanged;
        }
        private void Tokens_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)