private void OnMainStudentFormClosing(object sender, FormClosingEventArgs e) { MessageDialog messageDialog = new MessageDialog(@"Bạn thực sự muốn thoát?", MessageDialog.DialogType.YesNo); messageDialog.SendValueDelegate = delegate(MessageDialog.DialogResultType result) { if (result == MessageDialog.DialogResultType.No) { e.Cancel = true; } else if (result == MessageDialog.DialogResultType.Yes) { DatabaseCore.ReleaseConnect(); } }; messageDialog.ShowDialog(); }