Converting Directed Acyclic Graph (DAG) to tree

I'm trying to implement algoritm to convert Directed Acyclic Graph to Tree (for fun, learining, kata, name it). So I come up with the data structure Node:

/// <summary>
/// Represeting a node in DAG or Tree
/// </summary>
/// <typeparam name="T">Value of the node</typeparam>
public class Node<T> 
{
    /// <summary>
    /// creats a node with no child nodes
    /// </summary>
    /// <param name="value">Value of the node</param>
    public Node(T value)
    {
        Value = value;
        ChildNodes = new List<Node<T>>();
    }

    /// <summary>
    /// Creates a node with given value and copy the collection of child nodes
    /// </summary>
    /// <param name="value">value of the node</param>
    /// <param name="childNodes">collection of child nodes</param>
    public Node(T value, IEnumerable<Node<T>> childNodes)
    {
        if (childNodes == null)
        {
            throw new ArgumentNullException("childNodes");
        }
        ChildNodes = new List<Node<T>>(childNodes);
        Value = value;
    }

    /// <summary>
    /// Determines if the node has any child node
    /// </summary>
    /// <returns>true if has any</returns>
    public bool HasChildNodes
    {
        get { return this.ChildNodes.Count != 0; }
    }


    /// <summary>
    /// Travearse the Graph recursively
    /// </summary>
    /// <param name="root">root node</param>
    /// <param name="visitor">visitor for each node</param>
    public void Traverse(Node<T> root, Action<Node<T>> visitor)
    {
        if (root == null)
        {
            throw new ArgumentNullException("root");
        }
        if (visitor == null)
        {
            throw new ArgumentNullException("visitor");