Export Gridview to Excel Produces Blank XLS file - Gridview Inside Update Panel...

I have used this export code in a number of places with no problem, but now that the gridview is located inside an UpdatePanel, I'm getting blank excel sheets when it exports.

Where am I dropping the data?  I debugged and in the BtnExportGrid_Click subroutine, the gvProd gridview has a 0 row count, so it's dropping the data somewhere before it even gets into the GridViewExportUtil class.

Thanks for any ideas!
<asp:UpdatePanel ID="updList" runat="server">
                        <ContentTemplate>
 
<tr>
                    <td colspan="2">
                        <br />
                        <asp:Panel ID="pnlFilter" runat="server" CssClass="TextLabel" OnClick="LetterChanged">
                                <asp:LinkButton ID="lnk0" runat="server" Text="[0-9]" ></asp:LinkButton> 
                                <asp:LinkButton ID="lnkA" runat="server" Text="A" AutoPostBack="True"></asp:LinkButton>                                                                                                                    
                                <asp:LinkButton ID="lnkB" runat="server" Text="B" AutoPostBack="True"></asp:LinkButton>                                                                                                                    
                                <asp:LinkButton ID="lnkC" runat="server" Text="C" AutoPostBack="True"></asp:LinkButton>                                                                                                                    
                                <asp:LinkButton ID="lnkD" runat="server" Text="D" AutoPostBack="True"></asp:LinkButton>                                                                                                                    
                                <asp:LinkButton ID="lnkE" runat="server" Text="E" AutoPostBack="True"></asp:LinkButton>                                                                                                                    
                                <asp:LinkButton ID="lnkF" runat="server" Text="F" AutoPostBack="True"></asp:LinkButton>                                                                                                                    
                                <asp:LinkButton ID="lnkG" runat="server" Text="G" AutoPostBack="True"></asp:LinkButton>                                                                                                                    
                                <asp:LinkButton ID="lnkH" runat="server" Text="H" AutoPostBack="True"></asp:LinkButton>                                                                                                                    
                                <asp:LinkButton ID="lnkI" runat="server" Text="I" AutoPostBack="True"></asp:LinkButton>                                                                                                                    
                                <asp:LinkButton ID="lnkJ" runat="server" Text="J" AutoPostBack="True"></asp:LinkButton>                                                                                                                    
                                <asp:LinkButton ID="lnkK" runat="server" Text="K" AutoPostBack="True"></asp:LinkButton>                                                                                                                    
                                <asp:LinkButton ID="lnkL" runat="server" Text="L" AutoPostBack="True"></asp:LinkButton>                                                                                                                    
                                <asp:LinkButton ID="lnkM" runat="server" Text="M" AutoPostBack="True"></asp:LinkButton>                                                                                                                    
                                <asp:LinkButton ID="lnkN" runat="server" Text="N" AutoPostBack="True"></asp:LinkButton>                                                                                                                    
                                <asp:LinkButton ID="lnkO" runat="server" Text="O" AutoPostBack="True"></asp:LinkButton>                                                                                                                    
                                <asp:LinkButton ID="lnkP" runat="server" Text="P" AutoPostBack="True"></asp:LinkButton>                                                                                                                    
                                <asp:LinkButton ID="lnkQ" runat="server" Text="Q" AutoPostBack="True"></asp:LinkButton>                                                                                                                    
                                <asp:LinkButton ID="lnkR" runat="server" Text="R" AutoPostBack="True"></asp:LinkButton>                                                                                                                    
                                <asp:LinkButton ID="lnkS" runat="server" Text="S" AutoPostBack="True"></asp:LinkButton>                                                                                                                    
                                <asp:LinkButton ID="lnkT" runat="server" Text="T" AutoPostBack="True"></asp:LinkButton>                                                                                                                    
                                <asp:LinkButton ID="lnkU" runat="server" Text="U" AutoPostBack="True"></asp:LinkButton>                                                                                                                    
                                <asp:LinkButton ID="lnkV" runat="server" Text="V" AutoPostBack="True"></asp:LinkButton>                                                                                                                    
                                <asp:LinkButton ID="lnkW" runat="server" Text="W" AutoPostBack="True"></asp:LinkButton>                                                                                                                    
                                <asp:LinkButton ID="lnkX" runat="server" Text="X" AutoPostBack="True"></asp:LinkButton> 
                                <asp:LinkButton ID="lnkY" runat="server" Text="Y" AutoPostBack="True"></asp:LinkButton> 
                                <asp:LinkButton ID="lnkZ" runat="server" Text="Z" AutoPostBack="True"></asp:LinkButton> 
                                <asp:LinkButton ID="lnkAll" runat="server" Text="ALL" AutoPostBack="True"></asp:LinkButton>
					  <asp:Button ID="btnExportGrid" runat="server" CssClass="TextLabel" Text="Export List" ForeColor="Green" Height="22" OnClick="BtnExportGrid_Click" />
                        </asp:Panel>
 
                        <asp:Panel ID="pnlProdList" runat="server" Height="300px" Width="800px" ScrollBars="both">
                            <asp:HiddenField ID="hdnLetter" runat="server" />
                            <asp:GridView ID="gvProd" runat="server" BackColor="#EEEEEE" GridLines="horizontal" AllowSorting="false" CssClass="TextLabel" Width="780px"
                                AutoGenerateColumns="false" DataKeyNames="key" EnableViewState="false" >
                                <SelectedRowStyle BackColor="LightYellow" Font-Bold="true" />
                                <HeaderStyle BackColor="LightSlateGray" ForeColor="White" />
                                <AlternatingRowStyle BackColor="#DDDDDD" Font-Bold="false" />
                                <RowStyle Font-Bold="false" />                                
                                <Columns>                                                                        
                                    <asp:CommandField SelectText="Details." ShowSelectButton="true" />
                                    <asp:BoundField DataField="prodname" HeaderText="Name" SortExpression="prod" />
                                </Columns>                                                        
                            </asp:GridView>
                        </asp:Panel>
                       </ContentTemplate>
                        <Triggers>
                       <Triggers>
                          <asp:AsyncPostBackTrigger ControlID="lnk0" EventName="Click"></asp:AsyncPostBackTrigger>
                          <asp:AsyncPostBackTrigger ControlID="lnkA" EventName="Click"></asp:AsyncPostBackTrigger>
                          <asp:AsyncPostBackTrigger ControlID="lnkB" EventName="Click"></asp:AsyncPostBackTrigger>
                          <asp:AsyncPostBackTrigger ControlID="lnkC" EventName="Click"></asp:AsyncPostBackTrigger>
                          <asp:AsyncPostBackTrigger ControlID="lnkD" EventName="Click"></asp:AsyncPostBackTrigger>
                          <asp:AsyncPostBackTrigger ControlID="lnkE" EventName="Click"></asp:AsyncPostBackTrigger>
                          <asp:AsyncPostBackTrigger ControlID="lnkF" EventName="Click"></asp:AsyncPostBackTrigger>
                          <asp:AsyncPostBackTrigger ControlID="lnkG" EventName="Click"></asp:AsyncPostBackTrigger>
                          <asp:AsyncPostBackTrigger ControlID="lnkH" EventName="Click"></asp:AsyncPostBackTrigger>
                          <asp:AsyncPostBackTrigger ControlID="lnkI" EventName="Click"></asp:AsyncPostBackTrigger>
                          <asp:AsyncPostBackTrigger ControlID="lnkJ" EventName="Click"></asp:AsyncPostBackTrigger>
                          <asp:AsyncPostBackTrigger ControlID="lnkK" EventName="Click"></asp:AsyncPostBackTrigger>
                          <asp:AsyncPostBackTrigger ControlID="lnkL" EventName="Click"></asp:AsyncPostBackTrigger>
                          <asp:AsyncPostBackTrigger ControlID="lnkM" EventName="Click"></asp:AsyncPostBackTrigger>
                          <asp:AsyncPostBackTrigger ControlID="lnkN" EventName="Click"></asp:AsyncPostBackTrigger>
                          <asp:AsyncPostBackTrigger ControlID="lnkO" EventName="Click"></asp:AsyncPostBackTrigger>
                          <asp:AsyncPostBackTrigger ControlID="lnkP" EventName="Click"></asp:AsyncPostBackTrigger>
                          <asp:AsyncPostBackTrigger ControlID="lnkQ" EventName="Click"></asp:AsyncPostBackTrigger>
                          <asp:AsyncPostBackTrigger ControlID="lnkR" EventName="Click"></asp:AsyncPostBackTrigger>
                          <asp:AsyncPostBackTrigger ControlID="lnkS" EventName="Click"></asp:AsyncPostBackTrigger>
                          <asp:AsyncPostBackTrigger ControlID="lnkT" EventName="Click"></asp:AsyncPostBackTrigger>
                          <asp:AsyncPostBackTrigger ControlID="lnkU" EventName="Click"></asp:AsyncPostBackTrigger>
                          <asp:AsyncPostBackTrigger ControlID="lnkV" EventName="Click"></asp:AsyncPostBackTrigger>
                          <asp:AsyncPostBackTrigger ControlID="lnkW" EventName="Click"></asp:AsyncPostBackTrigger>
                          <asp:AsyncPostBackTrigger ControlID="lnkX" EventName="Click"></asp:AsyncPostBackTrigger>
                          <asp:AsyncPostBackTrigger ControlID="lnkY" EventName="Click"></asp:AsyncPostBackTrigger>
                          <asp:AsyncPostBackTrigger ControlID="lnkZ" EventName="Click"></asp:AsyncPostBackTrigger>
                          <asp:AsyncPostBackTrigger ControlID="lnkALL" EventName="Click"></asp:AsyncPostBackTrigger>
                          <asp:PostBackTrigger ControlID="btnExportGrid" /> 
                      </Triggers>
                                </Triggers>
                    </asp:UpdatePanel>
                    </td>
                </tr>
 
 
 
    Protected Sub BtnExportGrid_Click(ByVal sender As Object, ByVal args As EventArgs)
        GridViewExportUtil.Export("ProdList.xls", Me.gvProd)
    End Sub
 
 
 
 
Imports System
Imports System.Data
Imports System.Configuration
Imports System.IO
Imports System.Web
Imports System.Web.Security
Imports System.Web.UI
Imports System.Web.UI.WebControls
Imports System.Web.UI.WebControls.WebParts
Imports System.Web.UI.HtmlControls
 
 
Public Class GridViewExportUtil
 
    Public Shared Sub Export(ByVal fileName As String, ByVal gv As GridView)
        HttpContext.Current.Response.Clear()
        HttpContext.Current.Response.AddHeader("content-disposition", String.Format("attachment; filename={0}", fileName))
        HttpContext.Current.Response.ContentType = "application/ms-excel"
        Dim sw As StringWriter = New StringWriter
        Dim htw As HtmlTextWriter = New HtmlTextWriter(sw)
        '  Create a form to contain the grid
        Dim table As Table = New Table
        table.GridLines = gv.GridLines
        '  add the header row to the table
        If (Not (gv.HeaderRow) Is Nothing) Then
            GridViewExportUtil.PrepareControlForExport(gv.HeaderRow)
            table.Rows.Add(gv.HeaderRow)
        End If
        '  add each of the data rows to the table
        For Each row As GridViewRow In gv.Rows
            GridViewExportUtil.PrepareControlForExport(row)
            table.Rows.Add(row)
        Next
        '  add the footer row to the table
        If (Not (gv.FooterRow) Is Nothing) Then
            GridViewExportUtil.PrepareControlForExport(gv.FooterRow)
            table.Rows.Add(gv.FooterRow)
        End If
        '  render the table into the htmlwriter
        table.RenderControl(htw)
        '  render the htmlwriter into the response
        HttpContext.Current.Response.Write(sw.ToString)
        HttpContext.Current.Response.End()
    End Sub
 
    ' Replace any of the contained controls with literals
    Private Shared Sub PrepareControlForExport(ByVal control As Control)
        Dim i As Integer = 0
        Do While (i < control.Controls.Count)
            Dim current As Control = control.Controls(i)
            If (TypeOf current Is LinkButton) Then
                control.Controls.Remove(current)
                control.Controls.AddAt(i, New LiteralControl(CType(current, LinkButton).Text))
            ElseIf (TypeOf current Is ImageButton) Then
                control.Controls.Remove(current)
                control.Controls.AddAt(i, New LiteralControl(CType(current, ImageButton).AlternateText))
            ElseIf (TypeOf current Is HyperLink) Then
                control.Controls.Remove(current)
                control.Controls.AddAt(i, New LiteralControl(CType(current, HyperLink).Text))
            ElseIf (TypeOf current Is DropDownList) Then
                control.Controls.Remove(current)
                control.Controls.AddAt(i, New LiteralControl(CType(current, DropDownList).SelectedItem.Text))
            ElseIf (TypeOf current Is CheckBox) Then
                control.Controls.Remove(current)
                control.Controls.AddAt(i, New LiteralControl(CType(current, CheckBox).Checked))
                'TODO: Warning!!!, inline IF is not supported ?
            End If
            If current.HasControls Then
                GridViewExportUtil.PrepareControlForExport(current)
            End If
            i = (i + 1)
        Loop
    End Sub
End Class

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synapse88Asked:
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jinalCommented:
Hello ,

As you are usingi nside update panel.

Try to rebind grid inside export . It may solve your problem .

It may in this function

Protected Sub BtnExportGrid_Click(ByVal sender As Object, ByVal args As EventArgs)
// Write bind code over here.
        GridViewExportUtil.Export("ProdList.xls", Me.gvProd)
    End Sub

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synapse88Author Commented:
Hi learnedone, sorry i forgot about this thread.

i'll try the recommended solution and post back the results.

thanks
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