Wim   Apr 27, 1:27 am     show options

Newsgroups: microsoft.public.dotnet.framework.aspnet
From: "Wim" <wimverl...@gmail.com> - Find messages by this author
Date: 27 Apr 2005 01:27:26 -0700
Local: Wed,Apr 27 2005 1:27 am
Subject: Performance issue when dynamically populating a dropdownlist
from a hidden frame
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Hi Everyone,

I'm trying to speed up a Asp.net 1.1 applications' performance. The
application needs to run in an environment with little bandwith and
therefore pagesizes and roundtrip times shoud be brought back to a
minimum.

The application suffered from relatively large screens. A typical aspx
page was 500 Kbyte so page load times were in the order of 40 - 50
seconds. After unsufficient loading improvement using .net caching
techniques like outputcaching and partial caching (location=Client), I
went on the track of local (client-side) caching using hidden frames. I

furthermore changed the navigation (dropdown menu) to load the
userpages in another frame and added javascript to load the data from
the hidden frames into the controls. So far, a pretty standard
approach.

Some details of the pages and the loading techniques:
The data in the hidden frames is stored in javascript arrays (generated

on the server) and only needs to be posted once. The page loaded in the

hidden frame containing the data is about 200 KBytes. But the userpages

decreased about 70% or more in size!!!
To load the data into the dropdownlists I issue a client-side
parents.myframe.location="page­toload.aspx" when the user selects
"page
to load" from the menu. In "pagetoload.aspx" I stated an
onload="LoadControls()" in the form tag to populate the controls
automatically.

I hope somebody is still with me :-)

After several different approaches however, I cannot get the javascript

which loads the data to perform under 15 seconds, and of course I would

like to bring it back to 1 or 2 seconds.
The pages contain about 16 dropdownlists and some textboxes. Each
dropdownlist gets loaded with approximately 500 options, so we are
facing a load of about 8,000 options.

This brings me to my question: is the dynamic loading of dropdownlist
options in javascript given the number of options reasonable or can it
be done in much less time?
The way I add the options is pretty standard:

var Option
var Text
var Value
for (var i=0;i < parent.hiddenframe.arraywithte­xt.length; i++)
{
  Text = parent.hiddenframe.arraywithte­xt[i]
  Value = parent.hiddenframe.arraywithva­lue[i]
  Option = new Option(Text, Value)

parent.userframe.forms("Loaded­Page").items("dropdownlist").A­dd(Option)

}

Is there a way to speed things up? I tried to disable the dropdownlist
while loading but that does not deliver too much improvement, if any at

all...

Thanks a lot for reading, hope somebody has an idea!
Wim