listbox event generator

using SKYPE4COMLib;
using System.Runtime.InteropServices;

 List<string> online_users = new List<string>();
 IEnumerable<SKYPE4COMLib.User> users;


Update_listbox();
            listBox1.DataSource = online_users;



        public void Update_listbox()
        {
            users = skype.Friends.OfType<SKYPE4COMLib.User>();

            users
                .Where(u => u.OnlineStatus == TOnlineStatus.olsOnline)
                .OrderBy(u => u.Handle)
                .ToList()
                .ForEach(u =>  online_users.Add(u.Handle));
            Update();
           
        }