private void Doublons_Click(object sender, RoutedEventArgs e)
 {
     if (_doublons == null)
     {
         _doublons = new DoublonsView();
         _doublons.Show();
         _doublons.Closed += new EventHandler(setToNull);
     }
     else
     {
         _doublons.Focus();
     }
 }