At first you need to declare that your program will be using winRT libraries:
- Right-click on your yourProject, select Unload Project
- Right-click on your yourProject(unavailable) and click Edit yourProject.csproj
- Add a new property group:
<targetplatformversion>8.0</targetplatformversion>
- Reload project
- Add reference Windows from Windows > Core
Now you need to add this code:
using Windows.UI.Notifications;
and you will be able to send notifications using this code:
var toast = new ToastNotification(doc);
ToastNotificationManager.CreateToastNotifier().Show(toast);
Reference: How to call WinRT APIs in Windows 8 from C# Desktop Applications – WinRT Diagram