private IUser Convert(LdapEntry entry)
        {
            if (null == entry)
            {
                return(null);
            }

            User user = new User
            {
                DistinguishedName = entry.Dn,
                DisplayName       = entry.Attribute("displayName"),
                Email             = entry.Attribute("mail"),
                FirstName         = entry.Attribute("givenName"),
                LastName          = entry.Attribute("sn"),
                Username          = entry.Attribute("sAMAccountName"),
                Roles             = entry.ArrayAttribute("memberOf").Where(r => roles.Contains(r)).ToList()
            };

            return(user);
        }