I solved it :
<dx:aspxuploadcontrol id="ASPxUploadControl1" runat="server" xmlns:dx="#unknown">
OnFileUploadComplete="ASPxUploadControl1_FileUploadComplete"
FileUploadMode="OnPageLoad">
<clientsideevents fileuploadcomplete="function(s, e) {<br mode=" hold=" /> window.open(e.callbackData);<br mode=" /></dx:aspxuploadcontrol>
protected void ASPxUploadControl1_FileUploadComplete(object sender, FileUploadCompleteEventArgs e)
{
if (e.IsValid)
{
fileinfo = new System.IO.FileInfo(e.UploadedFile.FileName);
resfilename = MapPath(System.Web.Configuration.WebConfigurationManager.AppSettings["DocumentPath"].ToString()) + "\\" + fileinfo.Name;
e.UploadedFile.SaveAs(resfilename);
//Response.ContentType = "Application/pdf";
//Response.TransmitFile(resfilename);
//Response.End();
}
}