Gtk#和treeview:如何获得"选中"项目？

using Gtk;
using System;

public class TreeViewExample : Window
{
    public TreeViewExample() : base("TreeView Example")
    {
        SetDefaultSize(400, 200);

        VBox box = new VBox(false, 2);
        Add(box);

        TreeView treeView = new TreeView(new TreeStore(typeof(string)));
        box.PackStart(treeView, true, true, 0);

        TreeViewColumn column = new TreeViewColumn("Items");
        treeView.AppendColumn(column);

        CellRendererText textRenderer = new CellRendererText();
        column.PackStart(textRenderer, true);
        column.AddAttribute(textRenderer, "text", 0);

        TreeStore store = (TreeStore)treeView.Model;
        store.AppendValues("Item 1");
        store.AppendValues("Item 2");
        store.AppendValues("Item 3");

        treeView.Selection.Changed += Selection_Changed;
    }

    private void Selection_Changed(object sender, EventArgs e)
    {
        TreeView treeView = (TreeView)sender;
        TreeSelection selection = treeView.Selection;

        TreeIter iter;
        if (selection.GetSelected(out iter))
        {
            TreeModel model = treeView.Model;
            string item = (string)model.GetValue(iter, 0);
            Console.WriteLine("Selected item: " + item);
        }
    }

    protected override void OnDeleteEvent(EventArgs e)
    {
        Application.Quit();
        base.OnDeleteEvent(e);
    }

    public static int Main(string[] args)
    {
        Application.Init();

        TreeViewExample window = new TreeViewExample();
        window.ShowAll();

        Application.Run();

        return 0;
    }
}