Google contact api v3 authentication

Question

I try use new google contacts API. My task is simple - retrieve contacts from static(my personal) domain account. I register my application at APIs Console and get ClientId,ClientSecret So I try authenticate my application through .net(google SDK)

 RequestSettings settings = new RequestSettings(appName,login,password);
 ContactsRequest cr = new ContactsRequest(settings);
 Feed<Contact> contacts = cr.GetContacts();
 foreach (Contact entry in contacts.Entries)
 {
      ....
 }

This code works well, but Google said that we should use OAuth2 authentication at production scenario. I try different parameters at RequestSettings but at other variant I get 401(access denied). So my question what's the right way to auth through google API v3 at installed desctop application without using other accounts credentials.

Answer 1

Before start to work you should get auth token. For do this you should create link whitch user should open and grand access to your app. Than you should request for token with the code witch you get later. This mechanism described at https://developers.google.com/accounts/docs/OAuth2Login something like this:

        private const string GetTokenUrl = "https://accounts.google.com/o/oauth2/token";    
        private new bool Auth(bool needUserCredentionals = true)
        {
            var dic = new Dictionary<string, string>();
            dic.Add("grant_type", "authorization_code");
            dic.Add("code", ResponseCode);
            dic.Add("client_id", ApplicationId);
            dic.Add("client_secret", ApplicationSecret);
            dic.Add("redirect_uri", HttpUtility.UrlEncode(AppRedirectUrl));
            var str = String.Join("&", dic.Select(item => item.Key + "=" + item.Value).ToArray());
            var client = new WebClient();
            client.Headers.Add("Content-type", "application/x-www-form-urlencoded");
            string s;
            try { s = client.UploadString(GetTokenUrl, str); }
            catch (WebException) { return false; }
            catch (Exception) { return false; }
            AuthResponse response;
            try { response = JsonConvert.DeserializeObject<AuthResponse>(s); }
            catch (Exception) { return false; }
            Token = response.access_token;
            SessionTime = DateTime.Now.Ticks + response.expires_in;
            if (needUserCredentionals)
                if (!GetUserInfo()) return false;
            return true;
        }

        public class AuthResponse
        {
            public string access_token { get; set; }
            public string token_type { get; set; }
            public long expires_in { get; set; }
        }

ResponseCode it's a code what you should catch after user redirect from "access granting page" But this method is api 2 i guess... Maybe I'm wrong, who know