how to add serial number column in a gridview at runtime?

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" 
OnRowDataBound="GridView1_RowDataBound">
            <Columns>
                <asp:TemplateField HeaderText="sno">

                    <EditItemTemplate>
                        <asp:TextBox ID="TextBox1" runat="server">
</asp:TextBox>
                    </EditItemTemplate>
                    <ItemTemplate>

                        <asp:Label ID="Label1" runat="server">
</asp:Label>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:BoundField DataField="id" HeaderText="id" />

            </Columns>
        </asp:GridView>
 
 


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

            i += 1;
            Label lblsno = (Label)e.Row.FindControl("Label1");
            lblsno.Text = i.ToString();
            
        }

    }