private List<AdUser> GetUsers()
{
string filter = string.Format("(&(ObjectClass={0}))", "user");
// filter = "(&(instanceType=4))";
// string[] properties = new string[] { "fullname" };
DirectoryEntry adRoot = new DirectoryEntry("LDAP://" + DOMAIN, null, null, AuthenticationTypes.Secure);
DirectorySearcher searcher = new DirectorySearcher(adRoot);
searcher.SearchScope = SearchScope.Subtree;
searcher.ReferralChasing = ReferralChasingOption.All;
// searcher.PropertiesToLoad.AddRange(properties);
searcher.Filter = filter;
SearchResultCollection result = searcher.FindAll();
return (from SearchResult searchResult in result select GetUserFromEntry(searchResult.GetDirectoryEntry())).ToList();
}