accessing a Boundfield ID field from a gridview in order to update a table with a checkbox value.

[hazz]

given <asp:BoundField DataField="ID" SortExpression="ID" visible =
"True"></asp:BoundField>

how can I access this ID field from within a button click event. I had bound
a collection of busiess objects to the gridview and now I am trying to
figure out how to loop through the collection from within the gridview which
has upated checkbox items to update in the db.

<ItemTemplate>
<asp:CheckBox ID="chkSelect" runat="server" />
</ItemTemplate>

void btnUpdate_Click(object sender, EventArgs e)
{ ???

Thank you,
-Greg