Windows Phone 8.1: Change background on phone theme change (Application.Current.Resources is empty)

Question

I would like to detect theme change in my application so I can change the background image accordingly. Sadly the WP7 example that included

(Visibility)Application.Current.Resources["PhoneDarkThemeVisibility"] ==
Visibility.Visible

throws an exception saying:

An exception of type 'System.Runtime.InteropServices.COMException' occurred in mscorlib.ni.dll but was not handled in user code WinRT information:
Cannot find a resource with the given key.
Additional information: Unspecified error

On debugging it turns out that Application.Current.Resources has 0 elements.

I would be very happy if it would turn out that I messed up something, but on running the WP7 example (in a WP8.1 project) found here: How to apply theme resources for Windows Phone it resulted in the same exception as before.
Does anyone know a WP8.1 solution to my problem? :)

Additional info:
I tried using the above mentioned code in the OnNavigatedTo part, the page constructor and even tried using it in a button click, but they all yielded the same result.
Other things like the font colour actually change after changing the theme of the phone automatically.

Answer 1

Use following code if you are using windows phone 8.1(not windows phone 8.1 silverlight)

if (App.Current.RequestedTheme == ApplicationTheme.Dark)
       {}

hope this helps