<script type="text/javascript">


            function invoice(id) {
                var _idInvoice = id;

                $.ajax({
                    url: '@Url.Action("callInvoice", "Fatture")',
                    //url: url,
                    data: { id: _idInvoice },
                    dataType: 'JSON',
                    cache: false,
                    async: true,
                    type: "POST",
                    success: function (data) {
                        //alert("file:\\" + data.path);
                        //$("#form_download").attr('action', $("#form_download").attr('action') + "/?path=" + data.path);
                        //var a = document.getElementById('invisibleButton'); //or grab it by tagname etc
                        //a.href = 'file:\\\\' + data.path;

                        alert(x);
                        //document.getElementById('invisibleButton').href = "./FatturePdf/" + data.path;

                        //document.getElementById('invisibleButton').click();
                        //a.click();
                    },
                    error: function (xhr, status, exception) {

                        console.log("Error: " + exception + ", Status: " + status);

                    }
                });
            }

        </script>

[HttpPost]
        public ActionResult callInvoice(int id)
        {
            byte[] byteFile = createPDF(id);

            var fattura = (from f in db.Fatture where f.ID == id select f).SingleOrDefault();
            string filename = fattura.NFattura + "_" + fattura.codFiscale + ".pdf";


            string tmpPath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory + @"FatturePdf/");
            
            System.IO.File.WriteAllBytes(@tmpPath + "\\" + filename, byteFile);

            //tmpPath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory + @"FatturePdf/" + filename);

            tmpPath += filename;

            tmpPath = "ciao";
            return Json(new { path = tmpPath });
            //return tmpPath;
        }