Question

I have a process that creates a PDF. I want these PDF’s to be temporary and short lived. I want to be able to perform the following when the user clicks a button:

string CreatePDF()//returns fileName.pdf
PromptUserToDownloadPDF()
DeletePDF(fileName.pdf)

I want to avoid having to create a cleanup procedure and deal with any race conditions that arise from users concurrently creating PDF’s while running cleanup.

In winforms, I would synchronously prompt a user to download a file. How can I do a similar task in web?

UPDATE
Please note that I am using a 3rd party app to create the PDF’s (Apache FOP). Basically I (will) have a function that invokes the command line:

C:>fop “inputfile” “output.pdf”

So, in memory is not an option…that is unless I could somehow do like….

string CreatePDF()//returns fileName.pdf
string RecreatePDFInMemory()
DeletePDF(fileName.pdf)
PromptUserToDownloadPDF()

Answer 1

Something like this:

byte[] _pdfbytes = CreatePDF();
Response.ContentType = "application/pdf";
Response.AppendHeader("Content-Length", _pdfbytes.Length.ToString());
Response.BinaryWrite(_pdfbytes);

Since this creates the PDF in memory, you don’t need to worry about cleanup.

Edit for OP’s edit:

From within CreatePDF, You can use Path.GetTempFileName to create a temp file and execute “fop” to write to that file. Delete that file immediately before returning the byte[]. I recommend doing this delete inside of a finally block. However, “Fop” does support having its output piped to stdout. Having the CreatePDF function grab that is probably cleaner.