JavaScript+Asp.Net MVC5同时下载多个文件

前端同时启动多个下载任务（但是没有做压缩包下载）

前端JavaScript脚本：

var idList = [1,2,3];//要下载的列表
$.each(idList, function (index, item) {
    downloadURL("/File/GetPdf?id=" + item);
});

var count = 0;
var downloadURL = function downloadURL(url) {
    var hiddenIFrameID = 'hiddenDownloader' + count++;
	var iframe = document.createElement('iframe');
    iframe.id = hiddenIFrameID;
    iframe.style.display = 'none';
    document.body.appendChild(iframe);
	iframe.src = url;
}

后端：

//FileController

public ActionResult GetPdf(int id)
{
    string fileName = "文件名";
    string path = "/filepath/";//文件路径

    string url = path + fileName ;
    if (url.Contains(".pdf"))
    {
        return File(DownLoadFielToMemoryStream(url), "application/pdf", fileName);
    }
    else
    {
        return Content("<script>alert('文件格式错误')</script>");
    }
}

private static MemoryStream DownLoadFielToMemoryStream(string url)
{
    var wreq = HttpWebRequest.Create(url) as HttpWebRequest;
    HttpWebResponse response = wreq.GetResponse() as HttpWebResponse;
    MemoryStream ms = null;
    using (var stream = response.GetResponseStream())
    {
        Byte[] buffer = new Byte[response.ContentLength];
        int offset = 0, actuallyRead = 0;
        do
        {
            actuallyRead = stream.Read(buffer, offset, buffer.Length - offset);
            offset += actuallyRead;
        }
        while (actuallyRead > 0);
        ms = new MemoryStream(buffer);
    }
    response.Close();
    return ms;
}