async private void Login_Click(object sender, RoutedEventArgs e)
        {
            //// Do sign-in logic here and store your authentication token using the AppSettings class
            App.MyAppSettings.AuthTokenSetting = ServerApi.GetAuthTokenFromWebService();
            App.MyAppSettings.UserIdSetting    = ServerApi.GetUserIdFromWebService();

            // log existing bindings
            {
                ContactBindingManager manager = await ContactBindings.GetAppContactBindingManagerAsync();

                foreach (ContactBinding binding in await manager.GetContactBindingsAsync())
                {
                    Logger.Log("MainPage", "existing binding = " + binding.RemoteId);
                }
            }

            // Add contact bindings for every contact information that we get from the web service
            // This bindings will be automatically linked to existent phone contacts.
            // The auto-linking is based on name, email or phone numbers match.
            await CreateContactBindingsAsync();

            // log new bindings
            {
                ContactBindingManager manager = await ContactBindings.GetAppContactBindingManagerAsync();

                foreach (ContactBinding binding in await manager.GetContactBindingsAsync())
                {
                    Logger.Log("MainPage", "binding = " + binding.RemoteId);
                }
            }

            MessageBox.Show("Done!");
        }