สอบถามเรื่อง UpdatePanel กับ MasterPage ครับ เมื่อใช้ร่วมกับ MasterPage แล้วปุ่ม Button ไม่สามารถใช้งานได้ครับ

<%@ Page Language="VB" MasterPageFile="~/MasterPage.master" AutoEventWireup="true" CodeFile="Default8.aspx.vb" Inherits="Default8" title="Untitled Page" validateRequest="false" enableEventValidation="false" %>

<asp:Content ID="Content1" ContentPlaceHolderID="head" Runat="Server">
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">
   
      
          
            <asp:Timer ID="IntervalTimer"  runat="server" Interval="15000">
        </asp:Timer>
<asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional" ChildrenAsTriggers="true"  > 
 <Triggers>
            <asp:AsyncPostBackTrigger ControlID="IntervalTimer" EventName="Tick" />
        </Triggers>
            <ContentTemplate>
      <asp:GridView ID="Griddashboard" runat="server" AutoGenerateColumns="False" DataKeyNames="OrderId" OnPageIndexChanging="ShowPageCommand" AllowPaging="True" OnRowCreated="gridOffersPush_RowCreated"
                            Width="100%">
              <RowStyle HorizontalAlign="Center" />

              <Columns>
                  <asp:TemplateField HeaderText="Date">
                      <ItemTemplate>
                          <asp:Label ID="lbldate" runat="server" Text='<%# Eval("con_date") %>'></asp:Label>
                      </ItemTemplate>
                      <HeaderStyle Width="300px" />
                  </asp:TemplateField>
                  <asp:TemplateField HeaderText="Customer Branch">
                      <ItemTemplate>
                          <asp:Label ID="lbl_branch" runat="server" Text='<%# Eval("BranchId") %>'></asp:Label>
                      </ItemTemplate>
                      <HeaderStyle Width="180px" />
                  </asp:TemplateField>
                  <asp:TemplateField HeaderText="Order ID">
                      <ItemTemplate>
                          <asp:Label ID="lbl_order" runat="server" Text='<%# Eval("OrderId") %>'></asp:Label>
                      </ItemTemplate>
                      <HeaderStyle Width="180px" />
                  </asp:TemplateField>
                  <asp:TemplateField HeaderText="Status">
                      <ItemTemplate>
                          <asp:Label ID="lbl_status" runat="server" Text='<%# Eval("OrderStatus") %>'></asp:Label>
                      </ItemTemplate>
                      <HeaderStyle Width="180px" />
                  </asp:TemplateField>
                  <asp:TemplateField HeaderText="Update Status">
                      <ItemTemplate>
                          <asp:Label ID="lbl_update" runat="server" Text="" ></asp:Label>
                          <asp:Button ID="btnchg" runat="server" Text="" onclick="btnchg_Click1"  />
                             
                      </ItemTemplate>
                      <HeaderStyle Width="180px" />
                  </asp:TemplateField>
              </Columns>
             <PagerStyle HorizontalAlign="Right" />
   <PagerSettings Mode="NumericFirstLast" PageButtonCount="3" />
                  
          </asp:GridView>
  </ContentTemplate>
       
        </asp:UpdatePanel>
          
      
    
</asp:Content>

Imports System.Configuration
Imports System.Data
Imports System.Linq
Imports System.Web
Imports System.Web.Security
Imports System.Web.UI
Imports System.Web.UI.HtmlControls
Imports System.Web.UI.WebControls
Imports System.Web.UI.WebControls.WebParts
Imports System.Xml.Linq
Imports System.Data.SqlClient
Imports System.Data.OleDb
Partial Class Default8
    Inherits System.Web.UI.Page

    Dim conn As New ConnectDB
    Dim converd_date As New date_string

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
 
        Binddashboard()

    End Sub


    Private Sub Binddashboard()


        Dim sqlCommand As String

        sqlCommand = "SELECT *,convert(varchar,UserStatusDate,120) con_date FROM ORDERS,USERS WHERE USERS.UserId = ORDERS.UserId and  OrderStatus not in ('Waiting for Approved','Cancel')"


        Dim dtTemp As New DataTable
        dtTemp = conn.FillDataSet(sqlCommand)

      
        Griddashboard.DataSource = dtTemp
        Griddashboard.DataBind()

    End Sub
    Protected Sub ShowPageCommand(ByVal s As Object, ByVal e As GridViewPageEventArgs)
        Dim newPageIndex As Integer = e.NewPageIndex
        Griddashboard.PageIndex = newPageIndex
        Binddashboard()

    End Sub

    Protected Sub btnchg_Click(ByVal sender As Object, ByVal e As System.EventArgs)

        Dim btn As New Button
        btn = CType(sender, Button)

        Dim orderid As String
        orderid = Griddashboard.DataKeys(CType(btn.NamingContainer, GridViewRow).RowIndex).Values("OrderId")

    End Sub

    Protected Sub gridOffersPush_RowCreated(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewRowEventArgs) Handles Griddashboard.RowCreated
        UpdatePanel1.Update()
        Dim cmdShowOfferDetailsDoc, btn1 As Button
        cmdShowOfferDetailsDoc = CType(e.Row.FindControl("btnchg"), Button)
        btn1 = CType(e.Row.FindControl("Button1"), Button)
        Dim objSM As ScriptManager
        objSM = Me.Page.FindControl("ScriptManager1")

        If Not objSM Is Nothing And Not cmdShowOfferDetailsDoc Is Nothing Then
            objSM.RegisterPostBackControl(cmdShowOfferDetailsDoc)
            objSM.RegisterPostBackControl(btn1)
        End If

    End Sub
    
End Class