Windows 8 includes quite a number of new elements. In this section, you'll look at the new elements you are most likely to need early in your Windows 8 app development.
Earlier, you learned how Windows 8 allows an app bar to slide into your application from the bottom, and a nav bar to slide in from the top. By convention, these bars hold user actions and navigation options, as discussed in the UI conventions earlier.
Both of these visual elements are constructed from the same XAML element: the AppBar. This same element can be used in two different places.
You also learned how the root visual element for parts of your app will usually be the Page control or one of its subclasses. Page has two properties for specifying app bars: Page.BottomAppBar for the app bar, and Page.TopAppBar for the nav bar.
Both of these properties take an AppBar element. AppBar is just a container. You can think of it as a content control. The AppBar class just provides a surface to show when the user makes the proper gestures. All of the appearance and functionality inside the AppBar is up to you.
An app bar can have any elements on it. For simple app bars, the recommended arrangement of elements features two sets of buttons, one on the left side of the app bar, and one on the right. The left side is for operations or actions specific to an item currently shown in the view. The right side is for operations that apply to the application ...