/// <summary>
        /// 'New admin' button is clicked
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void NewAdmin_Button_Click(object sender, RoutedEventArgs e)
        {
            NewAdminWindow w = new NewAdminWindow();

            w.Closed += new EventHandler(w_Closed);
            w.Show();
        }
        /// <summary>
        /// "New admin" window is closed
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        void w_Closed(object sender, EventArgs e)
        {
            NewAdminWindow w = sender as NewAdminWindow;

            if (w.DialogResult == true)
            {
                ThreadPool.QueueUserWorkItem(StartWork_NewAdmin, w.NewAdmin);
            }
        }