This property can be set to a value between zero and one, where one represents the total height of the containing element.
For example, to situate the area such that it's top edge coincides with the center of the containing element, set this property to .5.
Target Platforms: Android 4.4+, iOS 8+
Development Environments: Visual Studio 2015+, Visual Studio for Mac Preview, Xamarin for Visual Studio 4.2+