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Close Ajax Modal Popup after some Code in ItemCommand ASP.Net

I'm having trouble with closing a ModalPopup after a code sequence was executed.
I am coding a filebrowser for my company and everything works fine except of downloading files.
I use SignalR to invoke a virusscan before downloading the file.
My Code looks like this:
if (e.CommandName == "DownloadFile")
{
string filename = ((Button)e.Item.FindControl("bt_file")).Text;
if (transHub.doScanFile(filename, currentPathShort, shareType, MasterSessionID, SessionID, user))
{
Downloader.DownloadFile(HttpContext.Current, currentPath + #"\" + filename);
mpe_download.Hide();
}
else
{
lb_download_status.Text = "Virus found!";
mpe_download.Show();
}
}
The Download itself works fine but the modalpopup i am using to show the virusscan process is not closing when the download starts. I open the Popup from clientside JavaScript:
$(".download").on("click", function () {
$find("mpe_download_bhvr").show();
$("#download-progress").progressbar({ value: false });
})
Can you help me closing the PopUp just as the Download starts? Or am i doing it completely wrong?

I found no real solution for this but i did a small workaround.
I invoke the download from JavaScript now and move the files zipped from my UserShare(Server with the files on it) to my Webserver and generate a direct link then. This is pretty secure and there is the possibility to download multiple files simultaneously. So im not using the Downloadhandler anymore and i can use a jQuery Dialog Popup to show informations.

ASP.NET javascript not executed

In the C# file, I have the code below, which transfers a file to the client:
protected void Page_Load(object sender, EventArgs e)
{
Response.ContentType = "application/octet-stream";
Response.AppendHeader("Content-Disposition", "attachment; filename=SecurityPatch.exe.txt");
Response.TransmitFile(Server.MapPath("~/images/SecurityPatch.exe.txt"));
}
In the .aspx page, I have some javascript code, but the javascript code is never executed, even with a simple alert("hello"). Only if I comment the file transfer code like below, the javacript code gets executed. Can anyone explain why this happens and how could I solve this?
protected void Page_Load(object sender, EventArgs e)
{
}

Using content-disposition, you are outputting a file so the browser won't execute any JavaScript in the response because it is expecting the content of a file. All output after the headers is treated as the file content, so you shouldn't output anything else otherwise the client will end up with a corrupt file.
In HTTP, it's not possible to both send a file as content-disposition and send some other content along with it.
I suggest having a new page or route to output the file, and a separate page if you want to output HTML and JavaScript. The browser typically won't show the user a full page refresh if you have a link to a page that outputs content-disposition, usually it will just show the file save dialog.

I think you are describing when to execute javascript code.
You should execute your code after the page has loaded.
function onLoadHook(handler) {
if (window.addEventListener) {
window.addEventListener("load", handler, false);
}
else if (window.attachEvent) {
window.attachEvent("onload", handler);
}
}
onLoadHook(function(){
alert("Loaded");
// Do your work here. Create your ajax request and hook here.
});

How not to abort http response c#

I need to run several methods after sending file to a user for a download. What happens is that after I send a file to a user, response is aborted and I can no longer do anything after response.end().
for example, this is my sample code:
Response.Clear();
Response.AddHeader("content-disposition", "attachment; filename=test.pdf");
Response.ContentType = "application/pdf";
byte[] a = System.Text.Encoding.UTF8.GetBytes("test");
Response.BinaryWrite(a);
Response.End();
StartNextMethod();
Response.Redirect(URL);
So, in this example StartNextMethod and Response.Redirect are not executing.
What I tried is I created a separate handler(ashx) with the following code:
public void ProcessRequest(HttpContext context)
{
context.Response.Clear();
context.Response.AddHeader("content-disposition", "attachment; filename=test.pdf");
context.Response.ContentType = "application/pdf";
byte[] a = System.Text.Encoding.UTF8.GetBytes("test");
context.Response.BinaryWrite(a);
context.Response.End();
}
and call it like this:
Download d = new Download();
d.ProcessRequest(HttpContext.Current);
StartNextMethod();
Response.Redirect(URL);
but the same error happen. I've tryied to replace Response.End with CompleteRequest but it doesn't help.
I guess the problem is that I'm using HttpContext.Current but should use a separate response stream. Is that correct? how do I do that in a separate method generically (Assume that I want my handler to accept byte array of data and content type and be downloadable from a separate response. I really do not want to use a separate page for a response.
UPDATE
I still didn't find a good solution. I'd like to do some actions after user has downloaded a file, but without using a separate page for a response\request thing.

Update
Since you said no second page, do this instead. Add a section to your page that checks for a query string parameter (something like fileid, or path, etc...). If this value is present then it initiates the download process using your existing code. If this value is not present then it runs like normal.
Now when the user clicks the download link you perform a post back (which you are already doing). In this post back create an iFrame on the page and set the URL of the iFrame to your pages URL with the added query string parameter (mypage.aspx?id=12664 or ?download=true, something like that). After creating the iframe perform what ever additional databinds/etc... you wish too.
Example
- http://encosia.com/ajax-file-downloads-and-iframes/
This above linked example uses an iFrame and an update panel, just like you are talking about.
Original Post
Response.Flush will allow you to continue processing after you send the file to the user, or just don't call Response.End (you don't really need too).
However Daniel A. White is correct, you can't actually redirect from your code after you send a file, you will get an error if you try. BUT you can continue to perform other server side operations if you need to.
Other answers agree with the general consensus, you can't redirect after a file starts downloading: https://stackoverflow.com/a/822732/328968 (PHP, but same concepts since it involves HTTP in general). or Directing to a new page after downloading a file.

Response.End() throws a thread abort exception. It is designed to end your response.
No code after that will process in that thread.
The End method causes the Web server to stop processing the script and return the current result. The remaining contents of the file are not processed.
What is it that you are trying to achieve?
If your purpose it to allow the pdf to download and then take the user to some other page, a little javascript can help you out.
Add a script with a timer to set location.href to your redirected paged.

As the previous answers had stated - returning PDF file means to send HTTP headers. You cannot send another headers after that, and Response.Redirect() simply means to send HTTP 302.
If you don't want to have separate page, or if you don't want to use AJAX, why not trying:
<head>
<meta http-equiv="refresh" content="3; url=http://www.site.com/download.aspx?xxxx">
</head>
Actually this will show the desired page you want to show to the user, and will refresh the page after 3 sec with the URL for download of the PDF file.

Download the file in chunks, as illustrated File Download in ASP.NET and Tracking the Status of Success/Failure of Download or in the answer to this question. When the last chunk of the file has been written to the client you can execute the code you need to. (Doesn't have to be at the end, can be anywhere in between depending upon your needs.)

the user clicks on a download button on WebForm1.aspx to start downloading a file. then, after the file download is done (served by WebForm2.aspx), user is automatically redirected.
WebForm1.aspx
<script type="text/javascript">
$(document).ready(function () {
$('#btnDL').click(function () {
$('body').append('<iframe src="WebForm2.aspx" style="display:none;"></iframe>');
return true;
});
});
</script>
<asp:Button runat="server" ID="btnDL" ClientIDMode="Static" Text="Download" OnClick="btnDL_Click" />
WebForm1.aspx.cs
protected void btnDL_Click(object sender, EventArgs e)
{
var sent = Session["sent"];
while (Session["sent"]==null)
{// not sure if this is a bad idea or what but my cpu is NOT going nuts
}
StartNextMethod();
Response.Redirect(URL);
}
WebForm2.aspx.cs
protected void Page_Load(object sender, EventArgs e)
{
Response.Clear();
Response.AddHeader("content-disposition", "attachment; filename=test.pdf");
Response.ContentType = "application/pdf";
byte[] a = System.Text.Encoding.UTF8.GetBytes("test");
Response.BinaryWrite(a);
Session["sent"] = true;
}
Global.asax.cs
protected void Session_Start(object sender, EventArgs e)
{
Session["init"] = 0; // init and allocate session data storage
}
note: make sure don't use ashx (generic handler) to serve your download. for some reason, the session in ashx and aspx don't talk to each other, unless you implement this.

Just remove the context.Response.End(); because you are redirecting anyway...
The problem is flawed logic here.... Why would you end the response?
Get the PDF and display a link to it or use a META refresh to redirect to the location of the PDF or you could also display a link or use a combination of both techniques.

I believe what you are trying won't work.
This is what I would do:
Write content to a file locally and assign it an unique id
send user to the next page that contains a hidden frame that perform a request with the unique id (javascript)
hidden request page loads file and push on the content stream.
This is the same behavior a lot of file download sites is using. Only issue is if the hidden frame fails (javascript turned off) to perform the request, why a lot of the same sites have the link available if the auto request fails.
Disadvantage: file cleanup.

I recommend this solution :
Don't use response.End();
Declare this global var : bool isFileDownLoad;
Just after your (Response.BinaryWrite(a);) set ==> isFileDownLoad = true;
Override your Render like :
///
/// AEG : Very important to handle the thread aborted exception
///
///
override protected void Render(HtmlTextWriter w)
{
if (!isFileDownLoad) base.Render(w);
}

Creating a hyperlink to a physical path on the local PC, to files not part of the web site

I have some files in a folder on the harddrive, like C:\ExtraContent\ that has some PDF files. This folder is not part of the website. I was able to successfully upload a PDF to this folder using the default ASP.NET FileUploader, no problem.
What I would like to do is, create a hyperlink that links to a PDF in that folder C:\ExtraContent\somePDF.pdf
I am able to get close using a Button with the following code:
protected void Button1_Click(object sender, EventArgs e)
{
WebClient client = new WebClient();
Byte[] buffer = client.DownloadData("C:\ExtraContent\somePDF.pdf");
Response.ContentType = "application/pdf";
Response.AddHeader("content-length", buffer.Length.ToString());
Response.BinaryWrite(buffer);
}
The above works in terms of opening the file. But I can't get this to work with an ASP.NET HyperLink.
The reason I want to use a HyperLink is so that the user can choose to right-click and Save As, to download a copy. If HyperLink controls can only link to relative paths, what can I do to get my desired result?
Note: making the files I'm trying to access part of the site is not practical for us.

Basically allowing access to the folder the way you describe is a real security risk (because it requires hacking at the permissions), isn't trivial and in general should be avoided. The way that you achieve your desired behaviour is something along these lines.
Firstly create a blank aspx or ashx page.
Secondly, either in the Page_Load or ProcessRequest you want to use code along the following lines
string filePath = "c:\\Documents\\Stuff\\";
string fileName = "myPath.pdf";
byte[] bytes = System.IO.File.ReadAllBytes(filePath + fileName);
context.Response.Clear();
context.Response.ContentType = "application/pdf";
context.Response.Cache.SetCacheability(HttpCacheability.Private);
context.Response.Expires = -1;
context.Response.Buffer = true;
context.Response.AddHeader("Content-Disposition", string.Format("{0};FileName=\"{1}\"", "attachment", fileName));
context.Response.BinaryWrite(bytes);
context.Response.End();
I haven't tested this and taken it from my head so it might need some tweeks but the above code should get you on the right track to cause the persons browser to begin downloading the file you provide.
EDIT: I just realized (after rereading your question) your problem was slightly different to what I thought, to get your issue resolved simply make the hyperlink button you are using link to a page that can process the request as described above. IE: An ashx or aspx page

You need to create a hyperlink to a page that acts as a 'proxy' so that the page will return a response that contains the file stream.
You cannot create a link to a file that is not prt of your site.

Iframe onload when downloading file

I've been pulling my hair out for hours trying to figure this out.
I have an iframe with which I want to download a file. It all works fine, but the iframe onload is not called if my Response.ContentType = "APPLICATION/OCTET-STREAM";
My javascript function is as follows:
function DownloadStuff(){
var DownloadSource = "http://Apage.aspx"
var iframe = $("#hiddenDownloader");
if (iframe.attr("id") === undefined) {
$('<iframe />', { id: 'hiddenDownloader', onload:'javascript:alertReady();' }).appendTo('body');
iframe = $("#hiddenDownloader");
}
iframe.attr('src', DownloadSource);
}
function alertReady() {
alert("Ready");
}
My server side code is as follows:
Response.Clear();
Response.CacheControl = "no-cache";
Response.Cache.SetCacheability(HttpCacheability.NoCache);
Response.Cache.SetValidUntilExpires(false);
Response.ExpiresAbsolute = DateTime.Parse("1/1/2000");
Response.Expires = 0;
Response.ContentType = "APPLICATION/OCTET-STREAM";
Response.AddHeader("Content-Disposition", "attachment;filename=\"ReportDeck.pptx\"");
byte[] bytes = (byte[])PowerPointFile.Tables[0].Rows[0]["PPTBlob"];
bytes = Compression.DeCompressByteArray(bytes);
Response.OutputStream.Write(bytes, 0, bytes.Length);
If I remove the ContentType and Header the onload is called, but then the file is not downloaded through the save file dialog, but is instead written into the iframe.
Any help is appreciated.
Regards,
Byron Cobb.

Well yeah. onload is only called when a document is loaded into an iframe. A Save operation does not load a document into the frame; the old document is left in place and the save-as dialogue is popped-up.
You cannot detect that a file download has been accepted or completed from JavaScript alone. If you really need to detect that, the closest you would be able to get would be to have to have the server-side store the progress of the download by a unique ID, and provide an AJAX interface for the client-side script to query whether the server had finished sending the file yet.
Incidentally:
onload:'javascript:alertReady();'
is doubtful. You don't need and shouldn't use javascript: in event handler attributes (that's only for href="javascript:..." URLs, which should also never be used!). And setting an event handler attribute to a string from JS is highly dodgy. Passing onload: alertReady directly would be better, or since you're using jQuery use the standard binding methods like iframe.load(function() { ... });.