How to get an instance of a page when you navigate to it in UWP

By default when navigating a frame to a page, UWP doesn't give you back a page instance. So the only way of passing parameters is to use the parameter parameter. But having an instance to the page can have many other benefits: For example it allows the child page to have custom events and the parent page can subscribe to them.

However Frame has an event called Navigated that can help us to write an extension method to get a reference to the actual instance:

using Windows.UI.Xaml.Media.Animation;
using Windows.UI.Xaml.Navigation;

namespace Windows.UI.Xaml.Controls
{
    public static class FrameExtensions
    {
        /// <summary>
        /// Navigates to a page and returns the instance of the page if it succeeded,
        /// otherwise returns null.
        /// </summary>
        /// <typeparam name="TPage"></typeparam>
        /// <param name="frame"></param>
        /// <param name="transitionInfo">The navigation transition.
        /// Example: <see cref="DrillInNavigationTransitionInfo"/> or
        /// <see cref="SlideNavigationTransitionInfo"/></param>
        /// <returns></returns>
        public static TPage Navigate<TPage>(
            this Frame frame,
            NavigationTransitionInfo transitionInfo = null)
            where TPage : Page
        {
            TPage view = null;
            void OnNavigated(object s, NavigationEventArgs args)
            {
                frame.Navigated -= OnNavigated;
                view = args.Content as TPage;
            }

            frame.Navigated += OnNavigated;

            frame.Navigate(typeof(TPage), null, transitionInfo);
            return view;
        }
    }
}

Suppose we have page called Page1:

public sealed partial class Page1 : Page
{
    public Page1()
    {
        this.InitializeComponent();
    }

    public void Init(string param1, int param2)
    {
        // Initialize the page
    }
}

You can navigate to it like so:

Page1 page = frame.Navigate<Page1>();
// You can now do stuff with the page
// for example pass in as many parameters as you want
page.Init("Hello World", 42);

Note: Page1.Init will be called after Page1.OnNavigatedTo and before Page1.Loading.

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