In this lesson, we begin the process of understanding how to utilize data in our app. We begin by looking at this from the GroupedItemsPage.xaml's perspective, and how it utilizes the CollectionViewSource to bind to a View Model provided in the LayoutAwarePage.cs. We talk about the DefaultViewModel object which implements IObservableMap and what that really means. Finally, we pick apart the SampleDataSource.cs and observe it's inheritance hierarchy and the purpose of each of the classes defined in that file. Download the entire series' source code