Global Backspace key handler for Windows 8.1 apps

backspace.cs

 Window.Current.CoreWindow.KeyUp += (_, args) =>
{
    if (args.VirtualKey == VirtualKey.Back)
    {
        var element = FocusManager.GetFocusedElement();
        if (element is TextBox || element is PasswordBox)
        {
            return; //do not disturb user when typing
        }
     
        var frame = (Frame)Window.Current.Content;
        if (frame.CanGoBack)
        {
            frame.GoBack();
        }
    }
};