RequestSettings rs = new RequestSettings("mioaccount", ConfigurationManager.AppSettings["gmailUsername"], ConfigurationManager.AppSettings["gmailPassword"]);
ContactsRequest cr = new ContactsRequest(rs);

Contact c = new Contact();

//Aggiungo la mail
EMail primaryEmail = new EMail("pippo@gmail.com");
primaryEmail.Primary = true;
c.Emails.Add(primaryEmail);

//Aggiungo il nome
c.Title = "Pippo Pippi";

//Aggiungo città
StructuredPostalAddress pa = new StructuredPostalAddress();
pa.City = "Milano";

c.PostalAddresses.Add(pa);

string gid = GetGroupID("Mio Gruppo");
GroupMembership gm = new GroupMembership();
gm.HRef = gid;
c.GroupMembership.Add(gm);

c.Content = "Aggiunto automaticamente dalla sincronizzazione";

/*
Feed<Contact> fc = cr.GetContacts();
cr.Insert(fc, c);
*/

Uri feedUri = new Uri(ContactsQuery.CreateContactsUri("mioaccount@gmail.com"));
cr.Insert<Contact>(feedUri, c);

Execution of request failed: http://www.google.com/m8/feeds/contacts/mioaccount@gmail.com/full
InnerException = {"Errore del server remoto: (400) Richiesta non valida."}