How to get selected filename using fileuploade control in Ajax Accordion control and update Panel?

<asp:UpdatePanel ID="Acc_UpdatePanel" runat="server" UpdateMode="Conditional">
            <ContentTemplate>
 
                   <My Accordion Panes>
 
<asp:UpdatePanel ID="FileUpPanel" runat="server" UpdateMode="Conditional">
                                            <ContentTemplate>
                                                      necessary lines....
                                             </ContentTemplate>
<Triggers>
                                                <asp:PostBackTrigger ControlID="btnUpload" />
                                            </Triggers>
                                        </asp:UpdatePanel>
 
 
                 </ContentTemplate>
</asp:UpdatePanel>

 if (FileUpload1.HasFile)
        {
               // Necessary codes
         }