Selecting / Deselecting all the CheckBoxes Inside a GridView

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

public partial class _Default : System.Web.UI.Page 
{
    protected void Page_Load(object sender, EventArgs e)
    {        
        if (!IsPostBack)
        {
            BindGridView();
        }
    }

    protected void BindGridView()
    {
        gvCheckboxes.DataSource = GetDataSource();
        gvCheckboxes.DataBind();
    }

    protected DataTable GetDataSource()
    {
        DataTable dTable = new DataTable();
        DataRow dRow = null;
        Random rnd = new Random();
        dTable.Columns.Add("sno");

        for (int n = 0; n < 10; ++n)
        {
            dRow = dTable.NewRow();

            dRow["sno"] = n + ".";

            dTable.Rows.Add(dRow);
            dTable.AcceptChanges();
        }

        return dTable;
    }

    protected void gvCheckboxes_RowCreated(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.DataRow && (e.Row.RowState == DataControlRowState.Normal || e.Row.RowState == DataControlRowState.Alternate))
        {
            CheckBox chkBxSelect = (CheckBox)e.Row.Cells[1].FindControl("chkBxSelect");
            CheckBox chkBxHeader = (CheckBox)this.gvCheckboxes.HeaderRow.FindControl("chkBxHeader");

            chkBxSelect.Attributes["onclick"] = string.Format("javascript:ChildClick(this,'{0}');", chkBxHeader.ClientID);
        }
    }
}