This .NET class wraps the AcDbGraphNode ObjectARX class. 

This class provides a generic graph node implementation. One other class is also involved in the graph mechanism: Graph. 

Detection for circular references is done by internally creating a duplicate set of references in each node, then trimming away all leaf nodes which terminate without circularity. If any nodes remain in the duplicate graph, those nodes exist in a cycle. Graph.FindCycles() is used to set up the internal cycle information and enable several query methods to return information about any cycles found.

Autodesk.AutoCAD.DatabaseServices.GraphNode
    Autodesk.AutoCAD.DatabaseServices.ObjectIdGraphNode
    Autodesk.AutoCAD.DatabaseServices.XrefGraphNode

Public Class GraphNode
Inherits DisposableWrapper

public class GraphNode : DisposableWrapper;

Graph, XrefGraph, XrefGraphNode