LDAP获取Win2K之前的登录名

Question

我想从LDAP查询所有用户，并获取用户的Windows 2000初始登录名，以便与外部数据进行比较。

我的代码是：

public GroupPrincipal GetGroup(string groupName)
{
    var principalContext = GetPrincipalContext();

    var groupPrincipal = GroupPrincipal.FindByIdentity(principalContext, groupName);
    return groupPrincipal;
}

public List<AdGroupMember> GetGroupMembers(string groupName)
{
    return (from member in GetGroup(groupName).GetMembers()
        let sad = member.GetUnderlyingObject() as DirectoryEntry
        let membreUpn = member as UserPrincipal
        select new AdGroupMember
        {
            MemberName = member.SamAccountName,
            RoleName = groupName,
            DomainName = member.UserPrincipalName ?? member.SamAccountName + "@" + member.Context.Name,
            UserGuid = member.Guid.HasValue ? member.Guid.Value.ToString() : new Guid().ToString(),
            FirstName = membreUpn.GivenName,
            LastName = membreUpn.Surname,
            Email = membreUpn.EmailAddress,
            Tel = membreUpn.VoiceTelephoneNumber,
            Title = membreUpn.GetProperty("title")
        }).ToList();
}

但结果并没有以MYDOMAIN \ User格式返回给我登录名，但是User@MYDOMAIN.com

例如，我有一个用户：crmadmin1，我想获得CRM2015 \ crmadmin1，这是win2K之前的登录名，但我只能获得crmadmin1@crm2015.constoso.com。

我怎样才能做到这一点？