internal class DirectoryManager
    {
        private static string makePath(string path, string searchPattern)
        {
            if (!path.EndsWith("\\"))
                path += "\\";
            return Path.Combine(path, searchPattern);
        }
 
        private static IEnumerable<string> getInternal(string path, string searchPattern, bool isGetDirs)

public bool IsADUsernameExistsAndNotDisabled(string userName)
    {
        DirectoryEntry searchRoot = new DirectoryEntry(ldapConnection, eCrewUserName, eCrewUserPassword);
  
        DirectoryEntry searchRoot = new DirectoryEntry("LDAP://999.999.999.999/DC=CompanyDomain, DC=com", "ADUserAdmin", "AdUserAdminPassword");
        DirectorySearcher searchForUser = new DirectorySearcher(searchRoot);
 
        searchForUser.SearchScope = SearchScope.Subtree;
        //searchForUser.Filter = string.Format("(&(objectCategory=Person)(anr={0}))", userName);
        //searchForUser.Filter = string.Format("(&(objectCategory=Person)(anr={0})(userAccountControl:1.2.840.113556.1.4.803:=2))", userName);