private void JoinElementsWindow_Closed(object sender, EventArgs e)
 {
     isShowned = false;
     selectElementsSelectOperation = SelectElementsToJoin.unsubscribe;
     currentExternalEvent.Raise();
     base.Close();
 }
 private void btnShowFirstElements_Click(object sender, RoutedEventArgs e)
 {
     FreezeUI();
     selectElementsSelectOperation = SelectElementsToJoin.showFirstSelectedElements;
     currentExternalEvent.Raise();
 }
 private void btnJoin_Click(object sender, RoutedEventArgs e)
 {
     FreezeUI();
     selectElementsSelectOperation = SelectElementsToJoin.join;
     currentExternalEvent.Raise();
 }