C#: Convert a tree node and sub nodes to text

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

namespace TreeToText
{
    class TreeToText
    {
        const string LineMid = "├─";
        const string LineLast = "└─";
        const string Line = "│  ";
        const string Space = "    ";

        /// <summary>
        /// Convert a tree node to text
        /// </summary>
        /// <param name="node">Root node to convert</param>
        /// <returns>Text</returns>
        public static string Tree2Text(TreeNode node)
        {
            if (node == null) return null;
            StringBuilder builder = new StringBuilder();
            builder.AppendLine(TreeNodeText(node));
            Tree2Text(builder, node, "");
            return builder.ToString();
        }

        static string TreeNodeText(TreeNode node)
        {
            return node.Text;
        }

        static void Tree2Text(StringBuilder builder, TreeNode parent, string prefix)
        {
            int nodesCount = parent.Nodes.Count;
            if (nodesCount == 0) return;
            int nodeMaxIndex = nodesCount - 1;
            for (int i = 0; i < nodesCount; i++)
            {
                builder.Append(prefix);
                TreeNode node = parent.Nodes[i];
                if (i != nodeMaxIndex)
                {
                    builder.Append(LineMid);
                    builder.AppendLine(TreeNodeText(node));
                    Tree2Text(builder, node, prefix + Line);
                }
                else
                {
                    builder.Append(LineLast);
                    builder.AppendLine(TreeNodeText(node));
                    Tree2Text(builder, node, prefix + Space);
                }
            }
        }
    }
}