problem with ajax file uploder when placed in a page containing update panel

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C#

ASP.NET

.NET

Ajax

.NET4

i have an AjaxFileuploder in a page which contain an update panel with a button.After pressing button file up loader is not working plz hep

<asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional">
    <ContentTemplate>
        <asp:Button ID="btnSubmit" runat="server" Text="Submit"
        onclick="btnSubmit_Click" />
    </ContentTemplate>
</asp:UpdatePanel>
</div>
<asp:AjaxFileUpload ID="AjaxFileUpload2" runat="server" />
<div class="clear"></div>

protected void btnSubmit_Click(object sender, EventArgs e)
  {
      UpdatePanel1.Update();
  }

plz help