public enum NodeType { Root, Parent, Child } Node rootNode = new Node(NodeType.Root); Node parentNode = new Node(NodeType.Parent); Node childNode = new Node(NodeType.Child);In this example, the NodeType enumeration is used to create a tree data structure with a root node, a parent node, and a child node. These nodes are created using the Node class, which takes a NodeType parameter to specify the type of the node. The package library used in this example is likely a custom library created by the programmer for their specific use case. However, there are several libraries available in C# for working with trees and graphs, such as the QuickGraph library and the Microsoft.Msagl package.