Microsoft.Phone.Controls.TransitionFrame.OnContentChanged C# (CSharp) Method

        protected override void OnContentChanged(object oldContent, object newContent)
        {
            base.OnContentChanged(oldContent, newContent);

            _contentReady = true;

            UIElement oldElement = oldContent as UIElement;
            UIElement newElement = newContent as UIElement;

            // Require the appropriate template parts plus a new element to
            // transition to.
            if (_firstContentPresenter == null || _secondContentPresenter == null || newElement == null)
            {
                return;
            }

            NavigationInTransition navigationInTransition = null;
            ITransition newTransition = null;

            if (newElement != null)
            {
                navigationInTransition = TransitionService.GetNavigationInTransition(newElement);
                TransitionElement newTransitionElement = null;
                if (navigationInTransition != null)
                {
                    newTransitionElement = _isForwardNavigation ? navigationInTransition.Forward : navigationInTransition.Backward;
                }
                if (newTransitionElement != null)
                {
                    newElement.UpdateLayout();

                    newTransition = newTransitionElement.GetTransition(newElement);
                    PrepareContentPresenterForCompositor(_newContentPresenter);
                }
            }

            _newContentPresenter.Opacity = 0;
            _newContentPresenter.Visibility = Visibility.Visible;
            _newContentPresenter.Content = newElement;

            _oldContentPresenter.Opacity = 1;
            _oldContentPresenter.Visibility = Visibility.Visible;
            _oldContentPresenter.Content = oldElement;

            if (_readyToTransitionToNewContent)
            {
                TransitionNewContent(newTransition, navigationInTransition);
            }
            else
            {
                _storedNewTransition = newTransition;
                _storedNavigationInTransition = navigationInTransition;
            }
        }