Question

I’m working on a web project that takes the results from a survey type application, and runs them through a bunch of calculations to come up with some recommended suggestions for the user.

Now, this calculation might take a minute or so, so I’d like to be able to give the user some update on it’s progress. Obviously, the quick and dirty solution would be to put up a message along the lines of “Please wait while we calculate your recommendations” with a spinning gear type graphic. (or whatever, you get the point..). Once the task completes, I’d redirect to the results page.

However, I’d like to do something a little more flashy. Maybe something along the lines of a progress bar, and even prompt the user with what’s going on in the background. For example, give them a progress bar, with some text that says “Now processing suggestion 3 of 15; Multi-Vitamin”

Any suggestions on how I could set this up? One way I’m thinking of doing it is to write the progress of the calculation method to the HttpContext, and slap up an update panel and timer that would show/refresh this info. I’ve also checked out maybe building a web service/method, and then poll that at some interval.

Has anybody done something similar to this before? What worked for you?

Thanks again!

~Jim

Answer 1

If you have never been to AjaxPatterns.org, then I would suggest a visit is in order. The relevant reading material you would be looking for is:

Progress Indicator

That covers several patterns to accomplish the goal along with the two you suggested already. If you want actual progress indication, then you are going to have to do a fair bit of work, but the basic pattern is as follows:

1. Kick off long running task (possibly on a seperate thread)
2. Create a shared resource that indicates work done, and a unique key that can retrieve that information. This can be done in-memory, database, file system…
3. Pass that key back to the client
4. On the client side, poll at some interval for progress updates using that key
5. Update the client display with progress indicator based on value
   returned.