สร้าง Checkbox ใน gridview ทำไงครับ ขอแบบละเอียดหน่อยนนะครับ

using System;
using System.Collections;
using System.Collections.Generic;
using System.Data;
using System.Diagnostics;
using System.Data.OleDb;

partial class _Default : System.Web.UI.Page
{

	OleDbConnection objConn;

	OleDbCommand objCmd;
	protected void Page_Load(object sender, System.EventArgs e)
	{
		string strConnString = null;
		strConnString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + Server.MapPath("~/App_Data/mydatabase.mdb") + ";";
		objConn = new OleDbConnection(strConnString);
		objConn.Open();

		if (!Page.IsPostBack()) {
			BindData();
		}
	}

	protected void BindData()
	{
		string strSQL = null;
		strSQL = "SELECT * FROM customer";

		OleDbDataReader dtReader = null;
		objCmd = new OleDbCommand(strSQL, objConn);
		dtReader = objCmd.ExecuteReader();

		//*** BindData to GridView ***'
		myGridView.DataSource = dtReader;
		myGridView.DataBind();

		dtReader.Close();
		dtReader = null;

	}

	protected void myGridView_RowDataBound(object sender, System.Web.UI.WebControls.GridViewRowEventArgs e)
	{

		if (e.Row.RowType == DataControlRowType.DataRow) {
			//*** CustomerID ***'
			Label lblCustomerID = (Label)e.Row.FindControl("lblCustomerID");
			if ((lblCustomerID != null)) {
				lblCustomerID.Text = e.Row.DataItem("CustomerID");
			}

			//*** Name ***'
			Label lblName = (Label)e.Row.FindControl("lblName");
			if ((lblName != null)) {
				lblName.Text = e.Row.DataItem("Name");
			}

			//*** Email ***'
			Label lblEmail = (Label)e.Row.FindControl("lblEmail");
			if ((lblEmail != null)) {
				lblEmail.Text = e.Row.DataItem("Email");
			}

			//*** CountryCode ***'
			Label lblCountryCode = (Label)e.Row.FindControl("lblCountryCode");
			if ((lblCountryCode != null)) {
				lblCountryCode.Text = e.Row.DataItem("CountryCode");
			}

			//*** Budget ***'
			Label lblBudget = (Label)e.Row.FindControl("lblBudget");
			if ((lblBudget != null)) {
				lblBudget.Text = Strings.FormatNumber(e.Row.DataItem("Budget"), 2);
			}

			//*** Used ***'
			Label lblUsed = (Label)e.Row.FindControl("lblUsed");
			if ((lblUsed != null)) {
				lblUsed.Text = Strings.FormatNumber(e.Row.DataItem("Used"), 2);
			}
		}
	}

	protected void Page_Unload(object sender, System.EventArgs e)
	{
		objConn.Close();
		objConn = null;
	}

	protected void Button1_Click(object sender, System.EventArgs e)
	{
		CheckBox CheckID = default(CheckBox);
		Label lblCustomerID = default(Label);
		int i = 0;
		Label1.Text = "";
		for (i = 0; i <= myGridView.Rows.Count - 1; i++) {
			CheckID = myGridView.Rows(i).FindControl("CheckID");
			lblCustomerID = myGridView.Rows(i).FindControl("lblCustomerID");
			if (CheckID.Checked == true) {
				//*** Have lblID.Text ***'
				this.Label1.Text = this.Label1.Text + "<br>" + lblCustomerID.Text;
			}
		}
	}
	public _Default()
	{
		Unload += Page_Unload;
		Load += Page_Load;
	}
}