单项选择题 You use Microsoft .NET Framework 4 to create a Windows Presentation Foundation (WPF) application. You add a ListBox to show grouped data. The ListBox is data-bound to a collection of items. Each item has the Name and State properties. You need to ensure that the ListBox meets the following requirements: Names grouped by State Names sorted in ascending order States sorted in descending order Which code fragment should you use?（）

单项选择题 You use Microsoft .NET Framework 4 to create a Windows Presentation Foundation (WPF) application. You add a ListBox control to the application. The ListBox control is data-bound to an instance of a custom collection class of the Product objects named ProductList. You need to ensure that changes to ProductList are automatically reflected in the ListBox control. What should you do? （）

单项选择题 You use Microsoft .NET Framework 4 to create a Windows Presentation Foundation (WPF) application. You add a ListBox control to the application. The ListBox control is data-bound to an instance of a custom collection class of the Product objects named ProductList. The number of items of the data-bound collection is fixed. However, users can modify the properties of each of the Product objects in the collection. You need to ensure that changes made on the Product objects are automatically reflected in the ListBox control. What should you do?（）