UWP Root frame vs Page frame

Question

Here is typical App.xaml.cs code

protected override void OnLaunched(LaunchActivatedEventArgs e)
    {
#if DEBUG
        if (System.Diagnostics.Debugger.IsAttached)
        {
            //this.DebugSettings.EnableFrameRateCounter = true;
        }
#endif
        rootFrame = Window.Current.Content as Frame;

        // Do not repeat app initialization when the Window already has content,
        // just ensure that the window is active
        if (rootFrame == null)
        {
            // Create a Frame to act as the navigation context and navigate to the first page
            rootFrame = new Frame();

            rootFrame.NavigationFailed += OnNavigationFailed;
            rootFrame.Navigated += OnNavigated;

            if (e.PreviousExecutionState == ApplicationExecutionState.Terminated)
            {
                //TODO: Load state from previously suspended application
            }

            // Place the frame in the current Window
            Window.Current.Content = rootFrame;

            // Register a handler for BackRequested events and set the
            // visibility of the Back button
            SystemNavigationManager.GetForCurrentView().BackRequested += OnBackRequested;

            SystemNavigationManager.GetForCurrentView().AppViewBackButtonVisibility =
                rootFrame.CanGoBack ?
                AppViewBackButtonVisibility.Visible :
                AppViewBackButtonVisibility.Collapsed;
        }

        if (e.PrelaunchActivated == false)
        {
            if (rootFrame.Content == null)
            {
                // When the navigation stack isn't restored navigate to the first page,
                // configuring the new page by passing required information as a navigation
                // parameter
                rootFrame.Navigate(typeof(SignInPage), e.Arguments);
            }
            // Ensure the current window is active
            Window.Current.Activate();
        }
    }

When rootFrame.Navigate(typeof(SignInPage), e.Arguments);is called, SignInPage is created. In SignInPage.xaml.cs, there might be code like: this.Frame.Navigate(typeof(FramePage));. Is the Frame from this.Frame. the same as rootFrame? If it is, when and where does the Page class get assigned the root frame from App.xaml.cs?

Answer 1

Yes this is the same Frame object, as the Page has a reference to the frame controlling it's content. In other words the Frame that did the navigation to the page.

Frame

Gets the controlling Frame for the Page content.

Source: learn.microsoft.com

This property is automatically set on navigation and is first available in your Page object in the OnNavigatedTo method.