ทำไม EditTemplate Textbox FindControl ยังได้ค่าเดิมผมทำ Gridview ใน ContentPlaceHolderid = MainContent

Dim txtEditName As TextBox = TryCast(GridView1.Rows(e.RowIndex).FindControl("txtName"), TextBox)

<%@ Page Language="VB" MasterPageFile="~/MoviePage.master" AutoEventWireup="false" CodeFile="Member.aspx.vb" Inherits="Member" title="Untitled Page" MaintainScrollPositionOnPostback ="true" %>

<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="cc1" %>

<%@ Register Assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
    Namespace="System.Web.UI" TagPrefix="asp" %>
<asp:Content ID="Content1" ContentPlaceHolderID="head" Runat="Server">
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" Runat="Server">
    <asp:ScriptManager id="ScriptManager1"
        runat="server"></asp:ScriptManager>
    <cc1:CalendarExtender ID="CalendarExtender1" runat="server" TargetControlID="Text_Birth" Format="dd/MM/yyyy" PopupButtonID="Image1">
    </cc1:CalendarExtender>
    &nbsp;&nbsp;<cc1:CalendarExtender ID="CalendarExtender2" runat="server" Format="dd/MM/yyyy"
        PopupButtonID="Image2" TargetControlID="Text_App">
    </cc1:CalendarExtender>
    &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
    <table style="width: 832px">