How not to abort http response c#

Question

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 any

Answer 1

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.

Answer 2

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.

Answer 3

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.)

Answer 4

I believe what you are trying won't work.

This is what I would do:

1. Write content to a file locally and assign it an unique id
2. send user to the next page that contains a hidden frame that perform a request with the unique id (javascript)
3. 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.

Answer 5

I recommend this solution :

1. Don't use response.End();

2. Declare this global var : bool isFileDownLoad;

3. Just after your (Response.BinaryWrite(a);) set ==> isFileDownLoad = true;

4. Override your Render like :

   /// /// AEG : Very important to handle the thread aborted exception /// /// override protected void Render(HtmlTextWriter w) { if (!isFileDownLoad) base.Render(w); }

Answer 6

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.