Remover usuário de Grupo AD c#

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Data;using System.Collections;using System.DirectoryServices;using System.IO;  namespace ADUsersFromGroup{    class Program    {        static ArrayList _userNames = new ArrayList();        static ArrayList _groupNames = new ArrayList();         static void Main(string[] args)        {            Console.WriteLine("Informe o nome do grupo AD e pressione ENTER: ");            string group = Console.ReadLine();            string ldap = Console.ReadLine();            ArrayList list = GetADGroupUsers(group, ldap);            using (StreamWriter sr = new StreamWriter("c:\\usuarios.txt", false))            {                foreach (var item in list)                    sr.WriteLine("{0}", item);            }            Console.WriteLine("********** FIM **********");        }          static ArrayList GetADGroupUsers(string groupName, string ldap)        {            SearchResultCollection results;            DirectorySearcher search = new DirectorySearcher(ldap);            search.Filter = String.Format("(cn={0})", groupName);            results = search.FindAll();            foreach (SearchResult result in results)            {                ResultPropertyCollection resultPropColl = result.Properties;                foreach (Object memberColl in resultPropColl["member"])                {                    DirectoryEntry gpMemberEntry = new DirectoryEntry("LDAP://" + memberColl);                    System.DirectoryServices.PropertyCollection userProps = gpMemberEntry.Properties;                    object objetoAD = userProps["sAMAccountName"].Value;                    if ((userProps["objectClass"].Value as object[]).Contains<object>("group"))                    {                        // valida se já percorremos este grupo                        if (!_groupNames.Contains(objetoAD))                        {                            _groupNames.Add(objetoAD.ToString());                            Console.WriteLine("Explodindo membros do grupo {0} ...", objetoAD);                            GetADGroupUsers(objetoAD.ToString());                        }                    }                    else                    {                        if (!_userNames.Contains(objetoAD))                        {                            _userNames.Add(objetoAD.ToString());                            Console.WriteLine("      Incluindo {0} ...", objetoAD);                        }                    }                }            }            return _userNames;        }    }}