public async Task<ActionResult> GetRefreshToken(string refreshToken)
        {
            var auth = new AuthenticationClient();
            await auth.TokenRefreshAsync(_consumerKey, refreshToken, _consumerSecret);

            ViewBag.Token = auth.AccessToken;
            ViewBag.ApiVersion = auth.ApiVersion;
            ViewBag.InstanceUrl = auth.InstanceUrl;
            ViewBag.RefreshToken = auth.RefreshToken;
            
            ViewBag.LoggedIn = true;

            return View("Index");
        }
        private async void btnRefreshToken_Click(object sender, RoutedEventArgs e)
        {
            try
            {
                var auth = new AuthenticationClient();
                await auth.TokenRefreshAsync(ConsumerKey, _token.RefreshToken);

                var message = string.Format("Token Refresh Successful:\n\nAccess Token: {0}\n\nInstance URL: {1}",
                        auth.AccessToken, auth.InstanceUrl);

                lblOutput.Text = message;
            }
            catch (ForceException ex)
            {
                lblOutput.Text = ex.Message;
            }
        }