How to change start page at startup?

Question

my application, currently, goes to the MainPage.xaml at startup (I don't know where it has configured though).

I want to be able to start with another page in some conditions. I think I can add this code to Application_Launching() in App.xaml.cs page:

NavigationService.Navigate(new Uri("/SecondPage.xaml", UriKind.Relative));

but NavigationService is not available in App.xaml.cs.

How can I start the application with another page if foo == true?

Answer 1

Changing start page in App.Xaml.cs:

private void Application_Launching(object sender, LaunchingEventArgs e)
{

        Uri nUri = new Uri("/SecondPage.xaml", UriKind.Relative);
        ((App)Application.Current).RootFrame.Navigate(nUri);

}

Setting static startup page in Property\WMAppManifest.xml file

<DefaultTask  Name ="_default" NavigationPage="SecondPage.xaml"/>

edit

Try it:

    private void Application_Launching(object sender, LaunchingEventArgs e)
    {
        Uri nUri = new Uri("/GamePage.xaml", UriKind.Relative);
        RootFrame.Navigate(nUri);
    }

and in Property\WMAppManifest.xml clear NavigationPage:

<DefaultTask  Name ="_default" NavigationPage=""/>