File Upload is not working in Update panel

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C#

ASP.NET

Hi all,

I have Update panel in Master page.But i cant access file upload control in aspx file.


Structure:

Masterfile

<div id="content" class="shell">
        <asp:UpdatePanel ID="UpdatePanel1" runat="server">
            <ContentTemplate>
                <asp:ContentPlaceHolder id="ContentPlaceHolder1" runat="server">

                </asp:ContentPlaceHolder>
            </ContentTemplate>
        </asp:UpdatePanel>
    </div>

File.aspx (it uses master file):

<asp:Content ID="Content3" ContentPlaceHolderID="ContentPlaceHolder1" runat="server">

<asp:UpdatePanel ID="RegUpdatePanel" runat="server">
                      <ContentTemplate>

<FileUpload ID="flUpload" runat="server" Width="148px" />
<triggers>
                            <asp:AsyncPostBackTrigger ControlID="btSubmit" EventName="Click" />
                            <asp:PostBackTrigger ControlID="lnkTemplate" />
                                 <asp:AsyncPostBackTrigger ControlID="btSubmit" />
                    </triggers>
 
                  
                    

if i use this code FileUpload control is not accessible

Pls help