Disable ASP.Net GridView Header CheckBox based on condition in C#

Hi all,

I need your help.

In my gridview I inserted a column that contains a checkbox in the header

<asp:TemplateField ItemStyle-HorizontalAlign="Center">
    <HeaderTemplate>
        <asp:CheckBox ID="chkBxHeader" Text="<br />Select"
            AutoPostBack="true" OnCheckedChanged="chkBxHeader1_CheckedChanged" runat="server" />
    </HeaderTemplate>
    <ItemTemplate>
        <div>
            <br />
            <asp:CheckBox ID="chkRow" runat="server" Enabled="false" />
            <asp:ImageButton ID="btnchkRow"
                ImageUrl="/img/checkbox_closed.gif"
                runat="server" />
        </div>
    </ItemTemplate>

Selecting this checkbox will perform the following procedure chkBxHeader1_CheckedChanged which follows the validation of the gridview rows

try
{
    CheckBox chkBxHeader = (CheckBox)sender;
    bool isvalid = false;
 
    foreach (GridViewRow row in gvProducts.Rows)
    {
        if (row.RowType == DataControlRowType.DataRow)
        {
            if (!(row.FindControl("chkRow") as CheckBox).Checked)
            {
                Page.ClientScript.RegisterStartupScript(this.GetType(), "Alert",
                    "alert('KO');", true);
                chkBxHeader.Checked = false;
                isvalid = false;
                break;
            }
            else
            {
                chkBxHeader.Checked = true;
                chkBxHeader.Enabled = false;
                isvalid = true;
            }
        }
    }
 
    // Process only if valid.
    if (isvalid)
    {
        Page.ClientScript.RegisterStartupScript(this.GetType(), "Alert",
            "alert('OK');", true);
    }
}
catch (Exception ex)
{
    Console.WriteLine("Skipped exception! " + ex);
}

If the procedure is successful i have to disable the checkbox in the column header, how can i do it?

I need to disable the checkbox in the column header of my gridview when only if the results count is 9.

I have tried this in GridView1_RowDataBound, without success:

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{     
    try
    {
        if (e.Row.RowType == DataControlRowType.DataRow ||
            e.Row.RowType == DataControlRowType.Header)
        {
            int counter = 0;

            foreach (GridViewRow row in GridView1.Rows)
            {
                CheckBox chkRow = (row.Cells[0].FindControl("chkRow") as CheckBox);

                if (chkRow.Checked)
                {
                    counter++;
                }
            }

            if (counter == 9)
            {
                CheckBox chkBxHeader = (CheckBox)e.Row.FindControl("chkBxHeader");
                Response.Write(counter + "<br />");
                chkBxHeader.Visible = false;
            }
        }
    }
    catch (Exception ex)
    {
        Console.WriteLine("Skipped exception! " + ex);
    }
}

Thanks in advance for any help or suggestion.