How can I update my app's Live Tile Badge in WP8?

[onno]

I hoped this code from page 549 of Nathan's "Windows 8 Apps with XAML and C#":\[code\] //string xmlString = @"<badge value='http://stackoverflow.com/questions/14416206/2'/>"; string xmlString = string.Format(@"<badge value=http://stackoverflow.com/questions/14416206/{0}/>", 42); XmlDocument document = new XmlDocument(); document.LoadXml(xmlString); BadgeNotification notification = new BadgeNotification(document); BadgeUpdateManager.CreateBadgeUpdaterForApplication().Update(notification);\[/code\]...would also work for WP8, but many of the classes are unrecognized in my WP8 ScheduledTaskAgent, namely XmlDocument, BadgeNotification, and BadgeUpdateManager.How can I accomplish the same thing in WP8 from my ScheduledTaskAgent?