de = new DirectoryEntry(string.Concat("LDAP://", LdapServerIPAddress, ":636", "/", "CN=", username, ",", LdapDistinguishedName), username, password, AuthenticationTypes.SecureSocketsLayer);                
dsearch = new DirectorySearcher(de);
dsearch.PropertiesToLoad.Add("memberof");
dsearch.Filter = String.Format("(&(objectClass=user)(sAMAccountName={0}))", username);
results = dsearch.FindOne();