BindableApplicationBar.BindableApplicationBar.OnPageNavigating C# (CSharp) Method

        void OnPageNavigating(object sender, System.Windows.Navigation.NavigatingCancelEventArgs e)
        {
            this.enabledStates = new Dictionary<BindableApplicationBarButton, BindingExpression>();
            if (!e.Uri.OriginalString.Contains("app://external/") && e.NavigationMode != System.Windows.Navigation.NavigationMode.Back)
            {
                foreach (var item in this.Buttons)
                {
                    this.enabledStates.Add(item, item.GetBindingExpression(BindableApplicationBarButton.IsEnabledProperty));
                    item.IsEnabled = false;
                }

                this.page.NavigationService.Navigating -= this.OnPageNavigating;
            }
        }