public static async Task <bool> IsAlreadyAuthenticated()
        {
            // Retrieve any stored account information
            var accounts = await AccountStoreFactory.Create().FindAccountsForServiceAsync(AppName);

            var account = accounts.FirstOrDefault();

            // If we already have the account info then we are set
            if (account == null)
            {
                return(false);
            }
            UpdateViewModel(account);
            return(true);
        }
        public static async Task FetchGoogleEmailAndPicture(Account account)
        {
            var request  = new OAuth2Request("GET", new Uri(Constants.UserInfoUrl), null, account);
            var response = await request.GetResponseAsync();

            if (response != null)
            {
                var userJson = response.GetResponseText();
                var user     = JsonConvert.DeserializeObject <User>(userJson);
                account.Username = user.Email;
                account.Properties[Constants.EmailAccountProperty] = user.Email;
                account.Properties[Constants.PhotoAccountProperty] = user.Picture;
                AccountStoreFactory.Create().Save(account, AppName);
                UpdateViewModel(account);
            }

            await Navigator.Current.AuthenticationComplete();
        }