Page navigation WP8.1

Question

I made an app to WP8 and I used the page navigation like NavigationService.Navigate(new Uri(...)) and worked well.
But now I'm trying to develop a WP8.1 app and can't figure out how is it going.
I get the following error The name 'NavigationService' does not exist in the current context.
I have two pages and I want to navigate between them.
How can I do?
What changed?

Answer 1

You can navigate using

Frame.Navigate(typeof(MainPage));

Answer 2

For Universal Apps (Windows Runtime), you need to use the Frame.Navigate(...) overload, with the type of the page you're navigating to.

To navigate to MainPage.xaml, you can use Frame.Navigate(typeof(MainPage));

I'll recommend reading Quickstart: Navigating between pages (Windows Runtime apps using C#/VB/C++ and XAML) (MSDN)