downloading PDF file

[unaltro2]

Hello, i'm trying simply to perform a download wuth the following code, but the PDF reader, once the file is downloaded, says something like "the file is corrupted" and it does not open it. So, the code is:

 <ext:Button ID="btnDoc1" runat="server" Flat="True" Text="Guida Operativa"  Icon="PageWhiteText" >
       <AjaxEvents >
              <Click OnEvent="mydownload" IsUpload="true" FormID="form1">
                      <EventMask ShowMask="false" MinDelay="500" Msg=""   />
                       <Confirmation  ConfirmRequest="True"  Title="Confirmation required..." Message=""></Confirmation> 
               </Click>
       </AjaxEvents>
</ext:Button>

and server side ( on 'mydownload' method):

mypdfFilePath = (HttpContext.Current.Server.MapPath("~\Docs\Guida Operativa.pdf"))

                      HttpContext.Current.Response.Clear()
                      HttpContext.Current.Response.ContentType = "Application/pdf"
                      HttpContext.Current.Response.AppendHeader("Content-Disposition", "attachment; filename = Guida Operativa.pdf")
                      HttpContext.Current.Response.AppendHeader("Content-Length", New FileInfo(mypdfFilePath).Length.ToString())
                      HttpContext.Current.Response.TransmitFile(HttpContext.Current.Server.MapPath(mypdfFilePath))
                      HttpContext.Current.Response.Close()
                      HttpContext.Current.Response.End()

with a classic asp.net button, it works; and the PDf file is not corrupted itself.

Anyone knows where i'm in fault?
Thanks in advance.

Fabio