Graph class

Graph.cs

/*
https://msdn.microsoft.com/en-us/library/ms379574(v=vs.80).aspx

An Extensive Examination of Data Structures Using C# 2.0

Visual Studio 2005
 
Scott Mitchell
4GuysFromRolla.com
Update January 2005
*/

public class Graph<T> : IEnumerable<T>
{
    private NodeList<T> nodeSet;

    public Graph() : this(null) {}
    public Graph(NodeList<T> nodeSet)
    {
        if (nodeSet == null)
            this.nodeSet = new NodeList<T>();
        else
            this.nodeSet = nodeSet;
    }

    public void AddNode(GraphNode<T> node)
    {
        // adds a node to the graph
        nodeSet.Add(node);
    }

    public void AddNode(T value)
    {
        // adds a node to the graph
        nodeSet.Add(new GraphNode<T>(value));
    }

    public void AddDirectedEdge(GraphNode<T> from, GraphNode<T> to, int cost)
    {
        from.Neighbors.Add(to);
        from.Costs.Add(cost);
    }

    public void AddUndirectedEdge(GraphNode<T> from, GraphNode<T> to, int cost)
    {
        from.Neighbors.Add(to);
        from.Costs.Add(cost);

        to.Neighbors.Add(from);
        to.Costs.Add(cost);
    }

    public bool Contains(T value)
    {
        return nodeSet.FindByValue(value) != null;
    }

    public bool Remove(T value)
    {
        // first remove the node from the nodeset
        GraphNode<T> nodeToRemove = (GraphNode<T>) nodeSet.FindByValue(value);
        if (nodeToRemove == null)
            // node wasn't found
            return false;

        // otherwise, the node was found
        nodeSet.Remove(nodeToRemove);

        // enumerate through each node in the nodeSet, removing edges to this node
        foreach (GraphNode<T> gnode in nodeSet)
        {
            int index = gnode.Neighbors.IndexOf(nodeToRemove);
            if (index != -1)
            {
                // remove the reference to the node and associated cost
                gnode.Neighbors.RemoveAt(index);
                gnode.Costs.RemoveAt(index);
            }
        }

        return true;
    }

    public NodeList<T> Nodes
    {
        get
        {
            return nodeSet;
        }
    }

    public int Count
    {
        get { return nodeSet.Count; }
    }
}