private void Add_Click(object sender, RoutedEventArgs e)
 {
     if (textBox.Text != "")
     {
         long id = _contentManager.AddTopic(textBox.Text, Convert.ToInt16(comboBox.SelectedValue));
         if (id > 0)
         {
             _topics.Add(_contentManager.GetComponent(id) as Topic);
             listBox.Items.Refresh();
             _saved                = false;
             Confirm.IsEnabled     = true;
             _empty                = false;
             EditLessons.IsEnabled = true;
         }
     }
 }