WPF Navigationservices transfer data

 public partial class deneme : Page

    {
        private string str;

        public deneme()
        {
            InitializeComponent();
            NavigationService.LoadCompleted += NavigationService_LoadCompleted1;
        }

        private void NavigationService_LoadCompleted1(object sender, NavigationEventArgs e)
        {
            string str = (string)e.ExtraData;

            MessageBox.Show(str);
        }
    }

private void click_event(object sender, RoutedEventArgs e)
        {
            deneme de = new deneme();
            NavigationService.Navigate(de, "string data");
        }