void goButton_Click(object sender, RoutedEventArgs e)
{
this.NavigationService.Navigate(new ContentPage(), DateTime.Now);
}
void NavigationService_LoadCompleted(object sender, NavigationEventArgs e)
{
DateTime requestDateTime = (DateTime)e.ExtraData;
string msg = string.Format("Request started {0}\nRequest completed {1}", requestDateTime, DateTime.Now);
MessageBox.Show(msg);
}