private void ChromelessWindow_Closing(object sender, System.ComponentModel.CancelEventArgs e) { object frameContent = Navigator.Frame.Content; PDFViewerPage page = frameContent as PDFViewerPage; ViewModel viewModel = null; if (page != null) { page.Unload(); viewModel = page.DataContext as ViewModel; page = null; } else { FrontPage frontPage = frameContent as FrontPage; viewModel = frontPage.DataContext as ViewModel; frontPage = null; } if (viewModel != null) { viewModel.Dispose(); } Navigator.Frame = null; }