Gets a value indicating whether the painted button's corresponding node is expanded.
true if the painted button's corresponding node is expanded; otherwise false.
Clicking a node button results in expanding/collapsing its corresponding node. By default, node buttons corresponding to expanded and collapsed nodes display '-' and '+' characters respectively. However, nodes can be painted using custom draw by handling the TreeList.CustomDrawNodeButton event. This event parameter's Expanded property allows you to distinguish between node buttons corresponding to expanded and collapsed nodes. Use this property to provide different painting for buttons corresponding to different node states.