/// <summary>
 /// Выбор изменяемого - тема/подтема
 /// </summary>
 /// <param name="sender"></param>
 /// <param name="e"></param>
 private void Button_Click(object sender, RoutedEventArgs e)
 {
     ThemSubChooser ch = new ThemSubChooser();
     ch.ShowDialog();
     
 }
        private void MenuItem_Click_7(object sender, RoutedEventArgs e)
        {
            MenuItem it = sender as MenuItem;
            ThemSubChooser th;

            if (it.Header.ToString() == "Изменить")
            {
                th = new ThemSubChooser(false);  
            }
            else
            {
                th = new ThemSubChooser(true);  
            }

            th.ShowDialog();
            
        }