Creating PDFs on the fly using AJAX & C#

Question

I have a web page.There is a link to generate pdf reports.When the user clicks on the link the pdf generation process should start.Since the file size of the generated pdf is huge(>15Mb) the user cannot wait & thus has to proceed ahead with his other activities.That means the following simultaneous things would be happening now

1. The PDF Generation process continues unabated
2. The user continues with browsing without any jolt
3. After the pdf generation is completed the user should receive an email containing the download link.

Basically the implementation is

1. User clicks on generate report button
2. Using AJAX I make a call to the c# function say generateReport()

The problem

1. When I do this the user is not allowed to perform anything unless & untill the entire process completes.Ofcourse he can click on different links but with no response because of the AJAX call still getting implemented

How do I achieve this.I am a dot net(framework 2.0) developer creating aspx web pages using C#.I use javascript & AJAX(AjaxPro) to get rid of the postback in typical ASP.NET web applications.

Answer 1

In cases like this, you might want to consider splitting your PDF generation code out into a separate service, which your AJAX code could interact with to kick off the PDF creation. Once the service has created the PDF file, the service can email the user with the relevant info.

The AJAX code would use remoting to communicate with the service.

Answer 2

The concept you have in creating the reports and having them emailed to the user is a good one.

The implementation of this should be quite simple on the client side, ie a basic call to indicate that a report needs to be created. ie save this to a table (report queue)

The actual creation of the report should not be triggered by any of the calls from the front-end directly, Create a service (Windows Service) that runs through the "report queue" generating the PDF files and sending the emails.

As an added option, assuming the PDF's are not destroyed (ie not an email only solution) an ajax popup could be created on the client where the user can then go to a reports page and download the already generated file.

Answer 3

You could try on a timer make an AJAX call to a Function isReportDone(), that in turn checks a repository for the PDF. For generating the PDF, I THINK you'll need to pass that task out of your normal Request-Response Thread. Either by calling a seperate Thread (Multi-threading is fun) to process it, or by passing the data out to a seperate service on the server.

These are just two ideas really I had a similar issue with generating a file from a DB that had to be forcibly downloaded. I ended up calling a seperate page, in a seperate window, that wrote the data to the response stream. It actually worked great until the customer's network blocked any and all popups.

Answer 4

1. User asks for report to be generated (clicks a button)
2. Page kicks off an async service call to GeneratePdf(args).
3. User sees a spinner of some sort while Pdf is being generated, that way they know something is happening.
4. Pdf is generated (iTextSharp might come in handy here).
5. Pdf is stored somewhere. Database blob field would be ideal, that way the webservice can just pass back the id of the new file. Failing that, pass a filename back to the ajax code.
6. Webservice async (see this one) complete event happens, ajax code throws up either a popup or redirects to a new page. Maybe you want to replace the spinner with a "Ready!" link.
7. Link to pdf report file is emailed to user.