ASP.Net Download file to client browser

Question

I'm writing a simple test page to download a text file from a browser on button click. I am getting a really strange error that I have never seen before. Any thoughts?

The error occurs on Response.End(); and the file never gets to the client browser

Code:

  string filePath = "C:\\test.txt";
  FileInfo file = new FileInfo(filePath);
  if (file.Exists)
  {
    Response.ClearContent();
    Response.AddHeader("Content-Disposition", "attachment; filename=" + file.Name);
    Response.AddHeader("Content-Length", file.Length.ToString());
    Response.ContentType = "text/plain";
    Response.TransmitFile(file.FullName);
    Response.End();
  }

Error:

Unable to evaluate expression because the code is optimized or a native frame is on top of the call stack.

remove the end, and try the Responce.Flush() and the Responce.ApplicationInstance.CompleteRequest(); — Aristos, Jan 17 '12 at 15:46
Good call, that stopped the exception from being thrown. But the code still completes without anything happening on the browser. ?? — tier1, Jan 17 '12 at 15:55

score 39 · Accepted Answer · edited Sep 06 '16 at 09:36

39

Try changing it to.

 Response.Clear();
 Response.ClearHeaders();
 Response.ClearContent();
 Response.AddHeader("Content-Disposition", "attachment; filename=" + file.Name);
 Response.AddHeader("Content-Length", file.Length.ToString());
 Response.ContentType = "text/plain";
 Response.Flush();
 Response.TransmitFile(file.FullName);
 Response.End();

edited Sep 06 '16 at 09:36

RousseauAlexandre

1,484
19
24

answered Jan 17 '12 at 15:55

Ashwin Chandran

1,417
13
11

Same as before, runs through the code and throws an exception on Response.End(). It seems weird that Response.TransmitFile executes ok but the file does not get transfered? – tier1 Jan 17 '12 at 16:10
1

@Ashwin: I'm trying this solution in my code-behind file (my issue is http://stackoverflow.com/questions/18599735/downloading-a-dynamic-file), but no matter where I attempt to call `TransmitFile()` or `WriteFile()` I keep getting an exception: **Server cannot set content type after HTTP headers have been sent.** Any suggestions? – Codes with Hammer Sep 04 '13 at 20:34
Response.End() throws an exception by nature. – yazanpro May 07 '14 at 15:24
This worked for our application which uses this method to allow users to download .svg files. – ahwm Jan 26 '16 at 00:28
1

`Response.Clear();` does the [same as](http://stackoverflow.com/a/9044607/641833) `Response.ClearContent();` Why have both? – Trisped Jul 15 '16 at 21:40
Can this be done with with a filestream? The user chooses the save location and then we stream the file to that location? – bgmCoder Jun 06 '17 at 18:08
how to use this in a asp webapi? – Andreas Dec 20 '17 at 12:56

score 8 · Answer 2 · answered Jul 25 '13 at 17:11

Just a slight addition to the above solution if you are having problem with downloaded file's name...

Response.AddHeader("Content-Disposition", "attachment; filename=\"" + file.Name + "\"");

This will return the exact file name even if it contains spaces or other characters.

ASP.Net Download file to client browser

2 Answers2

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