Q:

Where is Windows.UI.Xaml.Controls.SearchBox?

I can't add using Windows.UI.Xaml.Controls.SearchBox; to my Windows Store Application. Visual Studio doesn't seem to know what I'm talking about. It tells me that it doesn't exist in the namespace.

A:

A namespace is a collection of classes, to use one of the classes you need to reference the respective namespace.
Windows.UI.Xaml.Controls is namespace
SearchBox is a class
You need to add reference of Windows.UI.Xaml.Controls:
using Windows.UI.Xaml.Controls;

and create an object of Windows.UI.Xaml.Controls.SearchBox:
Windows.UI.Xaml.Controls.SearchBox sbox = new Windows.UI.Xaml.Controls.SearchBox();
this.Controls.Add(sbox); //this line will add it to your app page controls list

Here is the list of controls available in Windows.UI.Xaml.Controls namespace.

