Update MainWindow when Window2 Closed?

I have a two window application. I am opening windows2 from my mainwindow. I want to update the mainWindow (change text for example) when the window2 closed. How am I able to do that.

Here is my mainWindow

namespace WpfApplication1
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        Window2 secondForm;

        public MainWindow()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, RoutedEventArgs e)
        {
            secondForm = new Window2();
            secondForm.Show();
        }
    }
}