private void Button_Click(object sender, RoutedEventArgs e)
  {
   string uri = string.Format("/Pagina2.xaml?nomeParametro={0}", txtValor.Text);

   NavigationService.Navigate(new Uri(uri, uriKind.Relative));
  }

protected override void OnNavigatedTo(NavigationEventArgs e)
  {
   if (NavigationContext.QueryString["nomeParametro"] != null)
  txtParametro.Text = NavigationContext.QueryString["nomeParametro"];

 base.OnNavigatedTo(e);
}

private void Button_Click(object sender, RoutedEventArgs e)
{
    string parametro = txtValor.Text;
    this.Frame.Navigate(typeof(Pagina2), parametro);
}

protected override void OnNavigatedTo(NavigationEventArgs e)
{
    txtParametro.Text = (string)e.Parameter;
}