Gets or sets the anchor index.
IndexPath AnchorIndex { get; set; }
The anchor index holds the index of the item from which non-ranged keyboard selection will start, i.e. in a vertical list it will hold the item from which selection should be moved by pressing the up or down arrow key. This is usually the last selected item.
AnchorIndex is automatically set when selecting an item via SelectedIndex or Select(IndexPath).