getting proceed reports active directory

i'm perplexing proceed reports user by active directory, recursively.
so given user, i finish adult list users have chairman manager have chairman manager chairman manager ... eventually quarrel user manager.

my tide try rather slow:

private stationary collection<string> getdirectreportsinternal(string userdn, out enlarged elapsedtime)
{
    collection<string> outcome = new collection<string>();
    collection<string> reports = new collection<string>();

    stopwatch sw = new stopwatch();
    sw.start();

    enlarged allsubelapsed = 0;
    twine principalname = string.empty;

    controlling (directoryentry directoryentry = new directoryentry(string.format("ldap://{0}",userdn)))
    {
        controlling (directorysearcher ds = new directorysearcher(directoryentry))
        {
            ds.searchscope = searchscope.subtree;
            ds.propertiestoload.clear();
            ds.propertiestoload.add("directreports");
            ds.propertiestoload.add("userprincipalname");
            ds.pagesize = 10;
            ds.serverpagetimelimit = timespan.fromseconds(2);
            searchresult sr = ds.findone();
            (sr != null)
            {
                principalname = (string)sr.properties["userprincipalname"][0];
                foreach (string s sr.properties["directreports"])
                {
                    reports.add(s);
                }
            }
        }
    }

    (!string.isnullorempty(principalname))
    {
        result.add(principalname);
    }

    foreach (string s reports)
    {
        enlarged subelapsed = 0;
        collection<string> subresult = getdirectreportsinternal(s, out subelapsed);
        allsubelapsed += subelapsed;

        foreach (string s2 subresult)
        {
        result.add(s2);
        }
    }



    sw.stop();
    elapsedtime = sw.elapsedmilliseconds + allsubelapsed;
    relapse result;
}

essentially, duty takes renowned name quarrel (cn=michael stum, ou=test, dc=sub, dc=domain, dc=com), that, ds.findone() slow.

i found lot faster hunt userprincipalname. problem: sr.properties["directreports"] only list strings, distinguishedname, seems delayed hunt for.

i wonder, there quick proceed modify between distinguishedname userprincipalname? there faster proceed hunt user i wholly have distinguishedname work with?

edit: interjection answer! poison manager-field softened duty 90 seconds 4 seconds. here new softened code, faster some-more entertaining (note there many approaching bug elapsedtime functionality, nonetheless tangible core duty works):

private stationary collection<string> getdirectreportsinternal(string ldapbase, twine userdn, out enlarged elapsedtime)
{
    collection<string> outcome = new collection<string>();

    stopwatch sw = new stopwatch();
    sw.start();
    twine principalname = string.empty;

    controlling (directoryentry directoryentry = new directoryentry(ldapbase))
    {
        controlling (directorysearcher ds = new directorysearcher(directoryentry))
        {
            ds.searchscope = searchscope.subtree;
            ds.propertiestoload.clear();
            ds.propertiestoload.add("userprincipalname");
            ds.propertiestoload.add("distinguishedname");
            ds.pagesize = 10;
            ds.serverpagetimelimit = timespan.fromseconds(2);
            ds.filter = string.format("(&(objectcategory=user)(manager={0}))",userdn);

            controlling (searchresultcollection src = ds.findall())
            {
                collection<string> tmp = null;
                enlarged subelapsed = 0;
                foreach (searchresult sr src)
                {
                    result.add((string)sr.properties["userprincipalname"][0]);
                    tmp = getdirectreportsinternal(ldapbase, (string)sr.properties["distinguishedname"][0], out subelapsed);
                    foreach (string s tmp)
                    {
                    result.add(s);
                    }
                }
            }
          }
        }
    sw.stop();
    elapsedtime = sw.elapsedmilliseconds;
    relapse result;
}