private void btnExit_Click(object sender, RoutedEventArgs e) { //this.Close(); System.Windows.Forms.DialogResult dr; dr = MessageBox.ShowBox("MessageID18", BMC_Icon.Question, BMC_Button.YesNo); if (dr.ToString() == "No") { return; } else { //this.Visibility = Visibility.Hidden; App.Current.Shutdown(); instance = null; } }