private void btnInsert_Click(object sender, RoutedEventArgs e)
        {
            InsertWindow w1 = new InsertWindow(this);

            w1.Show();
            ShowContent();
        }
 private void btnUpdate_Click(object sender, RoutedEventArgs e)
 {
     InsertWindow w1 = new InsertWindow(this);
     w1.Show();
 }