Optimizing building trees from a database

using System;
using System.Collections;
using System.Data;

namespace BuildingTrees
{
	public class FastTree
	{
    private Hashtable nodeList = new Hashtable();

		public FastTree()
		{
		}

    public TreeNode LoadTree(DataView dataTree)
    {
      // Loop through all records in the dataview
      foreach (DataRowView dataNode in dataTree)
      {
        // Store the current record in some typed variables
        int nodeID = (int)dataNode["NodeID"];
        int parentNodeID = (int)dataNode["ParentNodeID"];
        string text = dataNode["NodeText"].ToString();

        // Check if the node was already created
        if (nodeList.Contains(nodeID))
        {
          // Yes, fill in the missing properties
          TreeNode node = (TreeNode)nodeList[nodeID];
          node.Text = text;
          // If the node is not a root node, and there's no parent yet, look up or create
          if (nodeID != parentNodeID && node.ParentNode == null)
          {
            TreeNode parentNode = null;
            // Check if the parentnode was already created
            if (nodeList.Contains(parentNodeID))
            {
              // Yes, so use that one
              parentNode = (TreeNode)nodeList[parentNodeID];
            }
            else
            {
              // The parentnode doesn't exist yet, so create a partial parentnode.
              parentNode = new TreeNode(parentNodeID, null);
              nodeList.Add(parentNodeID, parentNode);
            }
            node.ParentNode = parentNode;
          }
        }
        else
        {
          // New node, check if it's a root node
          if (nodeID == parentNodeID)
          {
            // Yes, so no need for looking up or creating a parentnode
            TreeNode node = new TreeNode(nodeID, null);
            node.Text = text;
            nodeList.Add(nodeID, node);
          }
          else
          {
            // New child node
            TreeNode parentNode = null;
            // Check if the parentnode was already created
            if (nodeList.Contains(parentNodeID))
            {
              // Yes, so use that one
              parentNode = (TreeNode)nodeList[parentNodeID];
            }
            else
            {
              // No, so create a partial parentnode.
              parentNode = new TreeNode(parentNodeID, null);
              nodeList.Add(parentNodeID, parentNode);
            }

            // Create the new node
            TreeNode node = new TreeNode(nodeID, parentNode);
            node.Text = text;
            nodeList.Add(nodeID, node);
          }
        }
      } 
     
      // Find the rootnode
      IDictionaryEnumerator nodeEnumerator = nodeList.GetEnumerator();
      while (nodeEnumerator.MoveNext())
      {
        TreeNode node = (TreeNode)nodeEnumerator.Value;
        if (node.ParentNode == null)
          return node;
      }

      // Return nothing if no rootnode was found
      return null;
    }
	}
}