How to get a valid DirectoryEntry?

Question

I am trying to read an LDAP directory entry in a C# console application and I somehow don't succeed. Setting up the connection works fine:

private static LdapConnection ldapConnection;

public static void Main()
{
    NetworkCredential credentials = new NetworkCredential("uid=admin,ou=system", "secret");
    ldapConnection = new LdapConnection("127.0.0.1:10389");
    ldapConnection.SessionOptions.ProtocolVersion = 3;
    ldapConnection.AuthType = AuthType.Basic;

    try
    {
        ldapConnection.Bind(credentials);
        Console.WriteLine("Ldap connection is created.");
    }
    catch (Exception e)
    {
        Console.WriteLine("\r\nUnexpected exception occurred:\r\n\t" + e.GetType() + ":" + e.Message);
        return;
    }

    //searchUsers();
    //getSchemaClassName();
}

I can even find me some users:

private static void searchUsers()
{
    string[] attrs = new string[] { "cn", "sn" };
    string[] followedBy = new string[] { " ", "\n" };
    var request = new SearchRequest("ou=users,ou=system", "(objectClass=*)", System.DirectoryServices.Protocols.SearchScope.Subtree, attrs);
    var response = (SearchResponse)ldapConnection.SendRequest(request);

    foreach (SearchResultEntry entry in response.Entries)
    {
        for (int i = 0; i < attrs.Length; i++)
        {
            if (entry.Attributes.Contains(attrs[i]))
            {
                Console.Write(entry.Attributes[attrs[i]].GetValues(Type.GetType("System.String"))[0] + followedBy[i]);
            }
        }
    }
}

But when I for example try to read a directory entry's schema classname, I find that the directory entry contains a bunch of errors. This is the code:

private static void getSchemaClassName()
{
    string path = "ldap://localhost:10389/cn=David,ou=users,ou=system"; //path is ok, points to an existing user
    DirectoryEntry de = new DirectoryEntry(path, "uid=admin,ou=system", "secret");
    Console.WriteLine("Schema classname:" + de.SchemaClassName); //breakpoint here
}

When I place a breakpoint on the "breakpoint here"-line and subsequently examine de properties, I find that Guid, Name, Options, Parent, SchemaClassName and some others display the "The directory service is unavailable" error. Which even makes sense to me, since ldapConnection isn't in any way involved in this code, whereas it is in searchUsers(). But I don't know how to connect this code to ldapConnection; every DirectoryEntry example I come across on the internet apparently works without the connection. How can I get this fixed?

Thx, Cooz

Edit:

Changing getSchemaClassName() to the following helped somewhat...

private static void getSchemaClassName()
{
    string path = "LDAP://localhost:10389/cn=David,ou=users,ou=system";
    DirectoryEntry de = new DirectoryEntry(path, "uid=admin,ou=system", "secret", AuthenticationTypes.None);
    Console.WriteLine("Schema classname:" + de.SchemaClassName); //breakpoint here
}

...but not enough. Now at first sight only the Guid and NativeGuid properties of de give a System.Runtime.InteropServices.COMException and the rest seems fine. de.SchemaClassName is "organizationalPerson". Perfect.

However, upon setting the breakpoint once again and expanding for example de.SchemaEntry.SchemaEntry, almost everything that becomes visible there throws said exception: Guid, Name, ObjectSecurity, Options, SchemaClassName, SchemaEntry... you name it. The code still is not much use to me. What might be the possible cause of all those errors and how can I get it fixed?