I have an ASP.NET page where a request is made and after a while server returns either new page or just file for download. I want to indicate on screen s that server is “Processing…” while it takes time before returning data.
To call javascript when user hits submit is easy. Also reload of page on Postback causes any “Processing…” indicators (some DIVs popping up at the top of page) to go away.
My problem is mostly cases when data returned by server is not a page but a file to store. How can I catch the moment that server started to return data, and run a javascript/remove “Processing” DIV ? Is it even a way to do so in case of reply of different mime type?
In which cases it is even possible?
There are a couple of ways to approximate what you’re trying to do with timers and assumptions about what happened, but to really do what you’re describing, you need to be polling the server for an indication that the download occurred.
What I would do is take the file, Response.WriteFile it, and then write a flag to some store, either a db, or the file system, or whatever, that uniquely identifies that the transaction has completed. On the client side, your script is polling the server, and on the server, the poll response is checking the store for the flag indicating that the download has occurred.
The key here is that you have to take finer control of the download process itself…merely redirecting to the file is not going to give you the control you need. If you need more specifics on how to accomplish any of these steps, let me know.