DropDownList Flicker, Rendering and Slow

I keep noticing a flicker on a dropdown with only three items in it. These three items don't change between postbacks, so why is the UpdatePannel rendering them again?

Also, there is a similar problem with listboxes:

UpdatePanel PartialRendering large ListBoxes
http://forums.asp.net/thread/1363249.aspx

and it looks like large listboxes and dropdowns are both taking a long time for the callback to complete. Any ideas?

Try setting the UpdatePanel's

Mode="Conditional"

to fix the UpdatePanel always rendering issue. As to flickering, not sure on that one. I haven't seen it personally, but it may be browser specific. Have you tried this in different browsers to see what the effect is?

Hi,

as Glav suggested, the DropDownList flickering is specific to IE6. It is an issue in how the browser renders boxed elements, and I think it has been fixed in IE7beta.
Regarding the rendering delay, it may be related to dynamic DOM manipulation (for a DropDownList inside an UpdatePanel, recall that it will be rendered and dynamically populated on every partial postback) thus this is not an Atlas-specific issue and also you may experience it on almost all browsers (but maybe IE will be slower than others).

Thanks Paul.

That works for a lot of things. The trouble is I have a robust, windows like UI with a lot of controls in a browser with various master-detail-detail-detail style panels, so:

In the simple case, having several conditional UpdatePanels handle several Controls each, the Triggers aren't too bad between UpdatePanels, but DropDownLists and ListBoxes within the same UpdatePanel still get re-rendered.

Thanks Garbin, that's good to know

I'm not manipulating the DropDownList at all. Even an empty list exhibits this behavior, but it does appear that Atlas is unnecessarily manipulating the DOM for DropDownLists and ListBoxes, so I would need to argue that this is anAtlas-specific issue.

I think DropDownList and ListBoxes still need a lot of work and hopefully it will at least get looked at for the Atlas August CTP, because right now they are ridiculously slow.

See my other post:

UpdatePanel PartialRendering large ListBoxes
http://forums.asp.net/thread/1363249.aspx

From my vantage, it's a big enough of an issue where I wouldn't even consider deploying any sites done with Atlas until this improves. Maxing out the CPU on a client for any length time is just not acceptable.

Best Regards,

Dan

Hi,

dbDan:

I'm not manipulating the DropDownList at all. Even an empty listexhibits this behavior, but it does appear that Atlas is unnecessarilymanipulating the DOM for DropDownLists and ListBoxes, so I would needto argue that this is anAtlas-specific issue.

are you referring to the flickering issue or the slow rendering? The first one is IE-specific, while I can't think of the second one as an Atlas-specific issue, since dynamically adding 5000 items to a ListBox using pure JavaScript (no Atlas) is slowing down IE, FireFox, Opera (I didn't test it on other browsers).

Hi Garbin,

I'm sure you're right about the flickering, but I haven't had a chance to check out IE 7 yet.

This post was intended to be more about "unnecessary" rendering which causes "slow" rendering to occur more often. I guess I'm looking for some way to tell the ScriptManager that certain triggers are to hide/unhide the entire panel or maybe even just one control only, so it could be a little smarter about things.

In any case, it doesn't matter if you create a ListBox with static HTML, with JavaScript or as a Databound ListBox. It originally renders fine. But if it's in an UpdatePanel with PartialRendering enabled, the callback has some serious problems.

This post is just part of the issue, what I consider the real problem is described better in my other post.

http://forums.asp.net/thread/1363249.aspx

It got a low priority. I should have called it the "Atlas Callback CPU Loop Hog" bug or something, to see if that would at least get a semi-low priority :)

So that leaves me wondering if there is a way to get this issue/problem escalated to the point where someone will at least look at to see if its a simple fix or not.

Thanks,

Dan

I have a little more info on this one. I did a release to a Windows 2003 staging server. Although the delay is still obvious, it isn't nearly as bad.

Changing from Debug to Release mode doesn't seem to improve these ListBox and DropDownList delays on my Windows XP development machine.

Hopefully this makes it easier to duplicate or narrow down the problem(s), but I'm not so sure they are entirely on the client side anymore.

I just did some conditional pop-up dialogs based on the data, so I have a temporary workaround demonstration purposes, so I'm moving on to other things.

Does anybody know if this is the best forum to be reporting Atlas bugs?

Thanks,

Dan

Hi,

you can report bugs in these forums or also in theMicrosoft Connect website.

Thanks Garbin

I added these two posts toMicrosoft Connect as:

Atlas PartialRender CPU Bound/Slow with ListBoxes and DropDownLists

https://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=178704

Atlas UpdatePanel Trigger for Visible/Hidden Controls

https://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=178708

BTW - Like theAtlas Weblog a lot.

Best Regards,

Dan