Question

I have a button that when clicked, will generate a PDF and write it out to the response.

This is the basic structure of the code:

try
{
    using(Stream stream = generatePdf())
    {
       var file = createFile(stream);
       file.Transmit(HttpContext.Current.Response);
    }
}
catch (Exception ex)
{
    // Handle exception
    // Display Error Message
}

The transmit method contains the following code:

response.AddHeader("Content-Disposition", String.Format("attachment; filename={0}", filename));
response.AddHeader("Content-Length", bytes.Length.ToString());
response.ContentType = "application/octet-stream";
response.BinaryWrite(bytes);

Downloading the file works fine, except that it doesn’t complete the postback.

If I were to throw an exception above file.Transmit, the error handling would work properly and I would see the message get displayed in my browser. However, if there is an exception after the file.Transmit then nothing happens. The user saves/opens the pdf and the page does not reload.

How can I make it so that the postback always completes, that way I can display an appropriate message to the user?

Answer 1

It sounds like you’re trying to make the response contain two parts: the page and the PDF. You can’t do that. Typically download pages start a download as a separate request when you’ve gone to them (via JavaScript, I believe), with a direct link just in case the JavaScript doesn’t work.

Any one HTTP request can only have one response.