If you want to display a notification while the application is not running (but when you are doing the wallpaper), I believe that this is what you want:
ShellToast toast = new ShellToast(); toast.Title = "My app"; toast.Content = "Hello from my app background task!"; toast.Show();
For some reason, this does not display anything if your application is already running. If you want to display a message, you can use MessageBox.Show () (if you are okay for the user to click OK), or you can use the Coding4Fun Tools referenced by Haider.
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