We're looking to build a couple of modules that have the potential to be fairly IO intensive (large queries with binary image data) and for scalability reasons I want to do this processing asynchronously. I know that I can call RegisterAsyncTask to do what I need it to, but because Default.aspx does have Async="True" even if I do this ASP will treat the page as a synchronous one.

We're trying very hard not to change any of the DNN core code, so I was wondering if there was a good reason (and I'm sure there is) why DNN's Default.aspx page is not tagged to handle asynchronous calls. I suppose I could IFrame some asynchronous page of my own, but I thought I'd ask the question.

i suspect it's because theres never been a request for it , and the capability did not exist before 2.0. Please feel free to log it as an enhancement request in the public issuetracker @ support.dotnetnuke.com , so we can evaluate it further.

Off the top of my head, I think the only con is that it add's an overhead (additional delegates) per page, so for people using syncronous only tasks it would not be a desirable change.

I believe you can also work around core changes by creating a httpmodule that hooks the prerender event, adds the async declaration to the page object. You can also set the sync timeout via web.config i.e

<system.web>
  <pages asyncTimeout="60" />
</system.web>
 

Alternatively, I'd suggest you consider creating a new page i.e. webservicecalls.aspx , designed for async tasks, and utilise that.

Cathal