private void OnAboutClosed(object sender, EventArgs e) 
 {
     this.about = null;
 }
        protected override void ExitThreadCore()
        {
            if (about != null)
            {
                about.Close();
                about = null;
            }

            notifyIcon.Visible = false;
            base.ExitThreadCore();
        }
 private void OnAbout(object sender, EventArgs e)
 {
     if (about == null)
     {
         about = new About();
         about.FormClosed += OnAboutClosed;
         about.Show();
     }
     else
     {
         about.Activate(); 
     }
 }