Ошибка поиска определенного пользователя в Active Directory с помощью метода C # FindAll

Я пытаюсь найти конкретного пользователя в Active Directory, использую метод FindAll. Когда я его вызываю, возникает ошибка. Как я могу решить эту проблему?

Это исключение, которое я получаю:

Необработанное исключение типа System.Runtime.InteropServices.COMException произошло в System.DirectoryServices.dll

    SearchResultCollection sResults = null;
    try
    {
        //modify this line to include your domain name
        string path = "LDAP://microsistemas.com";
        //init a directory entry
        DirectoryEntry dEntry = new DirectoryEntry(path);

        //init a directory searcher
        DirectorySearcher dSearcher = new DirectorySearcher(dEntry);

        //This line applies a filter to the search specifying a username to search for
        //modify this line to specify a user name. if you want to search for all
        //users who start with k - set SearchString to "k";
        dSearcher.Filter = "(&(objectClass=user))";

        //perform search on active directory
        sResults = dSearcher.FindAll();

        //loop through results of search
        foreach (SearchResult searchResult in sResults)
        {
            if (searchResult.Properties["CN&"][0].ToString() == "Administrator")
            {
                ////loop through the ad properties
                //foreach (string propertyKey in
                //searchResult.Properties["st"])
                //{

                //pull the collection of objects with this key name
                ResultPropertyValueCollection valueCollection =
                searchResult.Properties["manager"];

                foreach (Object propertyValue in valueCollection)
                {

                    //loop through the values that have a specific name
                    //an example of a property that would have multiple
                    //collections for the same name would be memberof
                    //Console.WriteLine("Property Name: " + valueCollection..ToString());
                    Console.WriteLine("Property Value: " + (string)propertyValue.ToString());

                    //["sAMAccountName"][0].ToString();
                }
                //}
                Console.WriteLine(" ");
            }
        }
    }
    catch (InvalidOperationException iOe)
    {
        //
    }
    catch (NotSupportedException nSe)
    {
        //
    }
    finally
    {

        // dispose of objects used
        if (sResults != null)
            sResults.Dispose();

    }
    Console.ReadLine();
}