private void Button_Click(object sender, RoutedEventArgs e)
 {
     foreach (Order order in DataSource.orders)
     {
         if (order.OrderKey == int.Parse(guestrequestkey.Text))
         {
             instance.AddCalendar(order.requete, order.unit);
             order.status = Status.MailSent;
             MailMessage mail = new MailMessage();
             mail.To.Add("*****@*****.**");
             mail.From       = new MailAddress(order.unit.Owner.MailAddress);
             mail.Subject    = "mailSubject";
             mail.Body       = order.ToString();
             mail.IsBodyHtml = true;
             SmtpClient smtp = new SmtpClient();
             smtp.Credentials = new System.Net.NetworkCredential("*****@*****.**", "mahonlev");
             smtp.EnableSsl   = true;
             try
             {
                 smtp.Send(mail);
             }
             catch (Exception ex)
             {
                 MessageBox.Show(ex.ToString());
             }
         }
     }
 }