Prism Sample 18-NavigationCallback

同17相比，在导航方法中增加了回调函数

private void Navigate(string navigatePath)
        {
            if (navigatePath != null)
                _regionManager.RequestNavigate("ContentRegion", navigatePath, NavigationComplete);
        }

        private void NavigationComplete(NavigationResult result)
        {
            System.Windows.MessageBox.Show(String.Format("Navigation to {0} complete. ", result.Context.Uri));
        }