public MainWindow()

        {

            InitializeComponent();

            this.Closing += MainWindow_Closing;

        }

        private void MainWindow_Closing(object sender, System.ComponentModel.CancelEventArgs e)

        {

            foreach (Window w in this.OwnedWindows)

            {

                if (w!=null)

                {

                    w.Close();

                }

            }

            MessageBox.Show("所有子窗口关闭完成。");

        }

        private void Button_Click(object sender, RoutedEventArgs e)

        {

            for (int i = ; i < ; i++)

            {

                SubWindow s = new SubWindow("sub window"+i.ToString());

                s.Owner = this;

                s.Show();

            }

        }