DataGridView - Can't sort with auto mode

[MC]

I'm stumped. From what I read on MSDN, the code below should allow
the user to click on the column headers to sort the grid
automatically. Can someone point out why it does not?

Craig

~~~

public partial class Form1 : Form
{
private ArrayList items;

public Form1()
{
InitializeComponent();
}

private void Form1_Load(object sender, EventArgs e)
{
dataGridView1.AutoGenerateColumns = false;
dataGridView1.SelectionMode =
DataGridViewSelectionMode.FullRowSelect;

items = new ArrayList();
items.Add(new Item(101, "Hammer"));
items.Add(new Item(102, "Nails"));
items.Add(new Item(103, "Saw"));

DataGridViewTextBoxColumn col;

col = new DataGridViewTextBoxColumn();
col.SortMode = DataGridViewColumnSortMode.Automatic;
col.Name = "ID";
col.DataPropertyName = "ID";
dataGridView1.Columns.Add(col);

col = new DataGridViewTextBoxColumn();
col.SortMode = DataGridViewColumnSortMode.Automatic;
col.Name = "Description";
col.DataPropertyName = "Description";
dataGridView1.Columns.Add(col);

dataGridView1.DataSource = items;
}

}

public class Item
{
private int id;
private string description;

public Item(int id, string description)
{
this.id = id;
this.description = description;
}

public int ID { get { return id; } }
public string Description { get { return description; } }
}