Invisionware library for working Directory Services
See sample code for how to use the DN and RDN classes
Invisionware library for working LDAP in an easier fashon
var connection = new LdapServerConnection { Server = "<LDAP Server Name or IP>" };
var connectionManager = new LdapConnectionManager(connection);
var accountManager = connectionManager.CreateAccountManager();
var results = accountManager.FindUsers("sanderson");
Console.WriteLine(results.First().AccountName);