Google+ API: How can I use RefreshTokens to avoid requesting access every time my app launches?

Question

I'm trying to use the Google+ API to access info for the authenticated user. I've copied some code from one of the samples, which works fine (below), however I'm having trouble making it work in a way I can reuse the token across app-launches.

I tried capturing the "RefreshToken" property and using provider.RefreshToken() (amongst other things) and always get a 400 Bad Request response.

Does anyone know how to make this work, or know where I can find some samples? The Google Code site doesn't seem to cover this :-(

class Program {     private const string Scope = "https://www.googleapis.com/auth/plus.me";      static void Main(string[] args)     {         var provider = new NativeApplicationClient(GoogleAuthenticationServer.Description);         provider.ClientIdentifier = "BLAH";         provider.ClientSecret = "BLAH";         var auth = new OAuth2Authenticator<NativeApplicationClient>(provider, GetAuthentication);          var plus = new PlusService(auth);         plus.Key = "BLAH";         var me = plus.People.Get("me").Fetch();         Console.WriteLine(me.DisplayName);     }      private static IAuthorizationState GetAuthentication(NativeApplicationClient arg)     {         // Get the auth URL:         IAuthorizationState state = new AuthorizationState(new[] { Scope });         state.Callback = new Uri(NativeApplicationClient.OutOfBandCallbackUrl);         Uri authUri = arg.RequestUserAuthorization(state);          // Request authorization from the user (by opening a browser window):         Process.Start(authUri.ToString());         Console.Write("  Authorization Code: ");         string authCode = Console.ReadLine();         Console.WriteLine();          // Retrieve the access token by using the authorization code:         return arg.ProcessUserAuthorization(authCode, state);     } } 

Answer 1

Here is an example. Make sure you add a string setting called RefreshToken and reference System.Security or find another way to safely store the refresh token.

    private static byte[] aditionalEntropy = { 1, 2, 3, 4, 5 };      private static IAuthorizationState GetAuthorization(NativeApplicationClient arg)     {         // Get the auth URL:         IAuthorizationState state = new AuthorizationState(new[] { PlusService.Scopes.PlusMe.GetStringValue() });         state.Callback = new Uri(NativeApplicationClient.OutOfBandCallbackUrl);          string refreshToken = LoadRefreshToken();         if (!String.IsNullOrWhiteSpace(refreshToken))         {             state.RefreshToken = refreshToken;              if (arg.RefreshToken(state))                 return state;         }          Uri authUri = arg.RequestUserAuthorization(state);          // Request authorization from the user (by opening a browser window):         Process.Start(authUri.ToString());         Console.Write("  Authorization Code: ");         string authCode = Console.ReadLine();         Console.WriteLine();          // Retrieve the access token by using the authorization code:         var result = arg.ProcessUserAuthorization(authCode, state);          StoreRefreshToken(state);         return result;     }      private static string LoadRefreshToken()     {         return Encoding.Unicode.GetString(ProtectedData.Unprotect(Convert.FromBase64String(Properties.Settings.Default.RefreshToken), aditionalEntropy, DataProtectionScope.CurrentUser));     }      private static void StoreRefreshToken(IAuthorizationState state)     {         Properties.Settings.Default.RefreshToken = Convert.ToBase64String(ProtectedData.Protect(Encoding.Unicode.GetBytes(state.RefreshToken), aditionalEntropy, DataProtectionScope.CurrentUser));         Properties.Settings.Default.Save();     }