chore(windows_ui): add example of sending a toast notification (#220)

packages/windows_ui/example/README.md

@@ -1,7 +1,9 @@
 ## Examples
 
-| Example       | Description                                      |
-| ------------- | ------------------------------------------------ |
-| [dialog.dart] | Demonstrates showing a MessageDialog to the user |
+| Example             | Description                                      |
+| ------------------- | ------------------------------------------------ |
+| [dialog.dart]       | Demonstrates showing a MessageDialog to the user |
+| [notification.dart] | Demonstrates sending a toast notification        |
 
 [dialog.dart]: https://github.com/dart-windows/dartwinrt/blob/main/packages/windows_ui/example/dialog.dart
+[notification.dart]: https://github.com/dart-windows/dartwinrt/blob/main/packages/windows_ui/example/notification.dart

packages/windows_ui/example/notification.dart

@@ -0,0 +1,32 @@
+// Copyright (c) 2023, Dart | Windows. Please see the AUTHORS file for details.
+// All rights reserved. Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+import 'package:windows_ui/windows_ui.dart';
+
+void main() async {
+  const applicationId = 'dartwinrt';
+  // Create a toast notifier
+  final toastNotifier =
+      ToastNotificationManager.createToastNotifierWithId(applicationId);
+  if (toastNotifier != null) {
+    final toastContent = ToastNotificationManager.getTemplateContent(
+        ToastTemplateType.toastText02);
+    if (toastContent != null) {
+      final xmlNodeList = toastContent.getElementsByTagName('text');
+      const title = 'Updates available';
+      const content = 'New updates have been found for this program.';
+      // Set the title on the toast notification
+      xmlNodeList.item(0)?.appendChild(toastContent.createTextNode(title));
+      // Set the content on the toast notification
+      xmlNodeList.item(1)?.appendChild(toastContent.createTextNode(content));
+
+      // Create a toast notification
+      final toastNotification =
+          ToastNotification.createToastNotification(toastContent);
+
+      // Show the toast notification
+      toastNotifier.show(toastNotification);
+    }
+  }
+}