WCF Paged Results & Data Export

Question

I've walked into a project that is using a WCF service for the data tier. Currently, when data is needed for a grid, all rows are returned and the results are bound to a grid and the dataset is stuffed into a session variable for paging/sorting/rebinding. We've already hit a max message size problem, so I'm thinking it's time to convert from fetch and cache to fetch only the current page.

Face value this seems easy enough, but there's a small catch. The user is allowed to export the entire result set at any point. This means that for grid viewing purposes fetching the current page is fine, but when they want to do an export, I still need to make a call for all data.

This puts me back into the max message size issue. What is the recommended approach for this type of setup?

We are currently using the wsHttpBinding...

Thanks for any assistance.

Answer 1

I think the recommended approach for large files is to use WCF streaming. I'm not sure the exact details for your scenario, but you could take a look at this as a starting point:

http://msdn.microsoft.com/en-us/library/ms789010.aspx

Answer 2

I would probably do something like this in your case

• create a service with a "paged" GetData() method - where you specify the page index and the page size as additional parameters. This should give you a nice clean interface for "regular" use, and that should not hit the maxMessageSize limits

• create a second service (or method) that would send all data - ideally, you could bundle that up into a ZIP file or something on the server, before sending it. If that ZIP file is still too large, you might want to check out WCF streaming for handling large files, as Andy already pointed out

The maxMessageSizeLimit is in place for a good reason: to avoid Denial of Service attacks where a WCF service would just get flooded with large messages and thus brought to its knees. If you can, always try to keep that in mind and don't just jack up the maxMessageSize to 2 GB - it might come back to bite you :-)