DirectoryEntry de = new DirectoryEntry(DC_LDAP_PATH, utente, vecchia, AuthenticationTypes.Secure);

                // Recupero il nodo utente

                DirectorySearcher deSearch = new DirectorySearcher();

                deSearch.SearchRoot = de;

                deSearch.Filter = "(&(objectClass=user)(SAMAccountName=" + utente + "))";

                deSearch.SearchScope = SearchScope.Subtree;

                SearchResult results = deSearch.FindOne();

                de = new DirectoryEntry(results.Path, utente, vecchia, AuthenticationTypes.Secure);

                // Eseguo il cambio password

                de.Invoke("ChangePassword", new object[] { vecchia, nuova });