Mine

// Sample
using System;
using System.Windows.Forms;
using System.Drawing;

public class TestForm : Form
{
        static void Main ()
        {
                Application.Run (new TestForm ());
        }
        public TestForm ()
        {
                ComboBox combo_box = new ComboBox ();
                combo_box.Location = new Point (10, 10);
                combo_box.Parent = this;
                combo_box.TextChanged += delegate (object o, EventArgs args)
                {
                        // This never gets called in Mono
                        Console.WriteLine ("OnTextChanged :: " + ((Control) o).Text);
                };
        }
}