Tree Iterators

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

namespace TreeIterator.Example
{
	public partial class MainForm : Form
	{
		private const string _TextLabel = "Other surnames starting with {0} :";

		public MainForm() {
			InitializeComponent();

			// Initialize all ToolTips
			foreach(TreeNode node in Enumerate()) node.ToolTipText = node.Name;

			// Initialize the ComboBox
			FillComboBox();

			// Initialize the text label
			this.label4.Text = string.Format(_TextLabel, "");
		}

		/// <summary>Fill the combo box with all the surnames the tree contains.</summary>
		private void FillComboBox() {
			this.comboBox1.Items.AddRange(Enumerate().OrderBy(node => node.Text).Select(node=>node.Text).ToArray());
			this.comboBox1.SelectedIndex = 0;
		}

		/// <summary>Returns an enumeration of the tree nodes, with a depth traversal.</summary>
		/// <returns>An enumeration on the nodes.</returns>
		private IEnumerable<TreeNode> Enumerate() {
			DepthTreeEnumerator<TreeNode> enumerator = new DepthTreeEnumerator<TreeNode>(new SurnameTreeNode(this.treeView1.Nodes[0]));
			foreach (SurnameTreeNode node in enumerator) yield return node.Node;
		}

		/// <summary>The user clicked the search button.</summary>
		private void ButtonSearch_Click(object sender, EventArgs e) {
			
			// Get the selected name
			string selectedname = this.comboBox1.SelectedItem.ToString();

			// Get the matching node
			TreeNode resultnode = Enumerate().Single(node => node.Text == selectedname);
			
			// Set the reult node text into the text box
			this.textBox1.Text = resultnode.FullPath;

			// Make the matching node visible
			this.treeView1.CollapseAll();
			Enumerate().Single(node => node.Text == selectedname).EnsureVisible();

			// Initialize the text label
			string letter = selectedname[0].ToString();
			this.label4.Text = string.Format(_TextLabel, letter);

			// Search all surnames starting with the same letter than the selected surname
			StringBuilder sb = new StringBuilder();
			foreach (TreeNode node in Enumerate().Where(node => node.Text.StartsWith(letter))) {
				sb.Append(node.Text).Append("; ");
			}

			// Set the result string into the text box
			this.textBox2.Text = sb.ToString();
		}
	}
}