Using .Net to call GoogleAPI to obtain the Google Task list failed

static void Main(string[] args)
        {
            // Register the authenticator. The Client ID and secret have to be copied from the API Access
            // tab on the Google APIs Console.
            var provider = new NativeApplicationClient(GoogleAuthenticationServer.Description);
            provider.ClientIdentifier = "272908629865.apps.googleusercontent.com";
            provider.ClientSecret = "4UmdiNDILOV5bv-qRQz2XUwA";
            var auth = new OAuth2Authenticator(provider, GetAuthentication);
            // Create the service and register the previously created OAuth2 Authenticator.
            var service = new TasksService(auth);
            TaskLists results = service.Tasklists.List().Fetch();
            foreach (TaskList list in results.Items)
            {
                Console.WriteLine(list.Title);
            }
        }
        private static IAuthorizationState GetAuthentication(NativeApplicationClient arg)
        {
            // Get the auth URL:
            IAuthorizationState state = new AuthorizationState(new[] { TasksService.Scopes.Tasks.ToString() });
            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);
        }