Populate TreeView from Simple "list"

using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Forms;

namespace TreeViewExample
{
   public partial class Form1 : Form
   {
      public class kData {   // instead of class you can use struct, but with some dificulties
         public int index;
         public int level;
         public string NodeText;
         public string OtherData;
         //public stData()  { } // here you can initialize variables
      };
      List<kData> L; // instead of list you can use array, but I prefer Lists

      public Form1() {
         InitializeComponent();
      }

      private void btnPopulate_Click(object sender, EventArgs e) {
         // take data from ListBox and store it to List
         string line;
         L = new List<kData>();
         for (int i = 0; i < lbData.Items.Count; i++)  {
            line = lbData.Items[i].ToString();
            L.Add(new kData());
            L[i].index = i;
            L[i].level = Convert.ToInt32(line.Substring(0,1));
            L[i].NodeText = line.Substring(2);
            L[i].OtherData = "some other data you might need";
         }

         populateBaseNodes();
      }

      public void populateBaseNodes()
      {
         int i;
         tvData.Nodes.Clear();
         tvData.BeginUpdate();

         for (i = 0; i < L.Count(); i++) {
            if (L[i].level == 0) {
               tvData.Nodes.Add(L[i].NodeText, L[i].NodeText);
               tvData.Nodes[tvData.Nodes.Count - 1].Tag = L[i];
            }
         }

         for (i = 0; i < tvData.Nodes.Count; i++)
            populateChilds(tvData.Nodes[i]);

         tvData.EndUpdate();
         tvData.Refresh();
      }

      public void populateChilds(TreeNode parentNode)  
      {
         kData parentRed = (kData)parentNode.Tag;

         for (int i = parentRed.index + 1; i < L.Count; i++) {
            if (L[i].level == (parentRed.level + 1)) {
               parentNode.Nodes.Add(L[i].NodeText, L[i].NodeText);
               parentNode.Nodes[parentNode.Nodes.Count - 1].Tag = L[i];
               populateChilds(parentNode.Nodes[parentNode.Nodes.Count - 1]);
            }
            if (L[i].level <= parentRed.level) break;
         }
      }
   }
}