Gets a XamlDirective for the Items directive from XAML.
Assembly: System.Xaml (in System.Xaml.dll)
An Items directive is a node representation wrapper around multiple object values within a surrounding object. See [MS-XAML] Section 5.3.1.
If you examine raw XAML node stream interpretations or visualizations, Items is sometimes seen in string form as _Items (note the leading underscore) and is within the XAML language XAML namespace (as notated by a preceding Namespace node).