表单提交获取下载状态

思路：1 当submit后 1.1 后台接受请求，开始处理，处理完成后，准备下载文件，下载时给客户端写入cookie信息
1.2 当submit后，后台在处理，前台在调用setInterview,间隔的获取后台相应写入到站点的cookie值，如果该值被写
入后，在前台是客运获取到的，说明下载成功了 2 下载成功后清楚cookie和计时器

前段代码

var VehicleNoPar = $("<input>");
        VehicleNoPar.attr("type", "hidden");
        VehicleNoPar.attr("name", "DownloadBookingIDs");
        VehicleNoPar.attr("value", DownloadBookingIdVal);
        form.append(VehicleNoPar);

        //将表单放置在web中 
        $("body").append(form);

        var interval = setInterval(
                function () {
                    var downloadSucess = getCookie("transReplayDownload");
                    if (downloadSucess != undefined && downloadSucess != null && downloadSucess == "transReplayDownloadVal") {

                        clearInterval(interval);
                        deleteCookie("transReplayDownload");

                        // 下载成功,刷新列表数据
                        SearchData();
                    }
                    else {
                        alert("下载中");
                    }
                },
                1000,
                null
            );

        //表单提交 
        form.submit();

后台代码

string userAgent = Request.ServerVariables["http_user_agent"].ToLower();
                if (userAgent.IndexOf("firefox", System.StringComparison.Ordinal) == -1)
                {
                    fileName = HttpUtility.UrlEncode(System.Text.Encoding.UTF8.GetBytes(fileName));
                }
                Response.AppendCookie(new HttpCookie("transReplayDownload", "transReplayDownloadVal"));
                Response.AppendHeader("Content-Disposition", "attachment;filename=" + fileName);
                Response.Charset = "GB2312";
                Response.ContentEncoding = System.Text.Encoding.UTF8;
                Response.ContentType = "application/ms-excel";
                Response.WriteFile(filePath);
                Response.End();