ldap filter for distinguishedName

dn is not an attribute. Only attribute types, OIDs, and names can be used in filters.

When you get the manager attribute, to get the attributes for the DN that is the manager, use the value of the manager attribute as the base object in a search request. Set the scope of the search to BASE, the filter to either (&) or (objectClass=*) and request the attributes required. Then transmit the search request to the server and interpret the response.