Check whether CheckBox in GridView is checked or not in C# and ASP.Net

Hello there,

I need check whether CheckBox in GridView is checked or not in c# and ASP.Net

I using this tutorial Implement CheckChanged event of CheckBox inside GridView in ASP.Net

I don't have error but check whether CheckBox in GridView is checked not working.

My code below, please help me, thank you

<asp:TemplateField ItemStyle-HorizontalAlign="Center">
     <HeaderTemplate>
         <asp:CheckBox ID="chkBxHeader"
             AutoPostBack="true" OnCheckedChanged="chkBxHeader_CheckedChanged" runat="server" />
     </HeaderTemplate>
     <ItemTemplate>
         <div>
             <asp:CheckBox ID="chkRow" runat="server" />
         </div>
     </ItemTemplate>
</asp:TemplateField>

protected void chkBxHeader_CheckedChanged(object sender, EventArgs e)
{
    try
    {
        foreach (GridViewRow row in GridView1.Rows)
        {
            if (row.RowType == DataControlRowType.DataRow)
            {
                CheckBox chkRow = (row.Cells[0].FindControl("chkRow") as CheckBox);
 
                if (chkRow.Checked)
                {
 
                }
                else
                {
                    Page.ClientScript.RegisterStartupScript(this.GetType(), "Alert", "alert('KO');", true);
                }
            }
        }
    }
    catch (Exception ex)
    {
        Console.WriteLine("Skipped exception! " + ex);
    }
}