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Listbox slows down when adding large number of items

Basically I have a listbox to which I add simple STRING items- I have a
progress bar which I increment whenever I populate another portion of the
complete set of items I wish to add. What I observe is that as more and more
are added, population of the list box takes longer and longer. ie the first
10th of the item set are added much much quicker than the last 10th. THis
occurs with about 40,000 listbox items. My worry is the listbox may
potenetially store many 100s of 1000s of items.

Is this a known feature of the standard listbox. I really want to use a
listbox control as it offers perfect functionality for what I need. Just
curious (worried) about the semi-exponentially increasing itel Add () time.

Many thanks.

--
Message posted via DotNetMonster.c om
http://www.dotnetmonster.com/Uwe/For...sharp/200606/1
Jun 8 '06 #1
14 18746
Try using the BeginUpdate/EndUpdate methods to see if that helps perf in
your situation.

--
Tim Wilson
..NET Compact Framework MVP

"Paul_Madde n via DotNetMonster.c om" <u21795@uwe> wrote in message
news:617a7b393a 0bc@uwe...
Basically I have a listbox to which I add simple STRING items- I have a
progress bar which I increment whenever I populate another portion of the
complete set of items I wish to add. What I observe is that as more and
more
are added, population of the list box takes longer and longer. ie the
first
10th of the item set are added much much quicker than the last 10th. THis
occurs with about 40,000 listbox items. My worry is the listbox may
potenetially store many 100s of 1000s of items.

Is this a known feature of the standard listbox. I really want to use a
listbox control as it offers perfect functionality for what I need. Just
curious (worried) about the semi-exponentially increasing itel Add ()
time.

Many thanks.

--
Message posted via DotNetMonster.c om
http://www.dotnetmonster.com/Uwe/For...sharp/200606/1

Jun 8 '06 #2
Paul:
40,000 items in a Listbox? You have got to be kidding, man! Why don't you
set something up with typeahead where the first few letters typed set up a
Sql call with

WHERE xyz LIKE ' +searchterm +'%'

and then just bring back the matching items?

Peter

--
Co-founder, Eggheadcafe.com developer portal:
http://www.eggheadcafe.com
UnBlog:
http://petesbloggerama.blogspot.com


"Paul_Madde n via DotNetMonster.c om" wrote:
Basically I have a listbox to which I add simple STRING items- I have a
progress bar which I increment whenever I populate another portion of the
complete set of items I wish to add. What I observe is that as more and more
are added, population of the list box takes longer and longer. ie the first
10th of the item set are added much much quicker than the last 10th. THis
occurs with about 40,000 listbox items. My worry is the listbox may
potenetially store many 100s of 1000s of items.

Is this a known feature of the standard listbox. I really want to use a
listbox control as it offers perfect functionality for what I need. Just
curious (worried) about the semi-exponentially increasing itel Add () time.

Many thanks.

--
Message posted via DotNetMonster.c om
http://www.dotnetmonster.com/Uwe/For...sharp/200606/1

Jun 8 '06 #3
Are you by chance dealing with a sorted list?

If so I would fully expect it to be O(log n) (doing binary searches) just to
figure out where it should put it and O(n) for the copy that must occur on
adds :. After the finding of the location to insert O(log n) (binary search)
I would expect an O(n) operation to copy every passed it in the array.

example ... (indexes on left, values on right)

my array is
0 1
1 3
2 4
3 5
4 6
5 7

insert 2 ...

I now have to copy 3-7 (moving them up a spot) to make room for 2

0 1
1 ?
2 3
3 4
5 6
6 7

I then place my value at the second spot in the array ending up with

0 1
1 2
2 3
3 4
5 6
6 7
If this is the case you can make it much more efficient by adding all the
items, then sorting them using the Sort() method. This will only sort the
list once as opposed to 40k array copies :) ...

Cheers,

Greg Young
MVP - C#
http://geekswithblogs.net/gyoung
"Paul_Madde n via DotNetMonster.c om" <u21795@uwe> wrote in message
news:617a7b393a 0bc@uwe...
Basically I have a listbox to which I add simple STRING items- I have a
progress bar which I increment whenever I populate another portion of the
complete set of items I wish to add. What I observe is that as more and
more
are added, population of the list box takes longer and longer. ie the
first
10th of the item set are added much much quicker than the last 10th. THis
occurs with about 40,000 listbox items. My worry is the listbox may
potenetially store many 100s of 1000s of items.

Is this a known feature of the standard listbox. I really want to use a
listbox control as it offers perfect functionality for what I need. Just
curious (worried) about the semi-exponentially increasing itel Add ()
time.

Many thanks.

--
Message posted via DotNetMonster.c om
http://www.dotnetmonster.com/Uwe/For...sharp/200606/1

Jun 8 '06 #4
"Paul_Madde n via DotNetMonster.c om" <u21795@uwe> wrote in message
news:617a7b393a 0bc@uwe...
This occurs with about 40,000 listbox items. My worry is the listbox may
potenetially store many 100s of 1000s of items.


This is a joke, right...?
Jun 8 '06 #5
This is a general reply to all those who have so far helped.

No, no joke, my ListBox could well end up withover 1,000,000 elements. The
ListBox functionality is exactly what I need. It is a perfetc control for how
I wish to manage/display my data. It's just the Add () spped degradation
which is a real bummer.

Have in place Begin(End Update () calls so no improvement.

Am NOT using a sorted list.

If anyone has the unction to try it, simply add, in a tight loop, STRING
element items, say 500+ characters each, and notice how it takes ever longer
to add as the Count increases.

Any more suggestions would be greatly appreciated and thanks once more for
the help so far,

Paul

--
Message posted via http://www.dotnetmonster.com
Jun 9 '06 #6
"Paul_Madde n via DotNetMonster.c om" <u21795@uwe> wrote:
This is a general reply to all those who have so far helped.

No, no joke, my ListBox could well end up withover 1,000,000 elements. The
ListBox functionality is exactly what I need. It is a perfetc control for how
I wish to manage/display my data. It's just the Add () spped degradation
which is a real bummer.
How do your users feel about scrolling through a list with a million
elements? How long does it take for them to read all the possibilities?
Any more suggestions would be greatly appreciated and thanks once more for
the help so far,


I don't think you're going about this the right way at all. I'd try and
make a user interface somewhat similar to the old index lookup in
WinHlp32.exe - as you type a value in, it zooms in on the location. If
the contents must be presented as a listbox, then make the listbox
virtual, so that only the visible elements are actually loaded. It
doesn't look like the .NET listbox can be made virtual (the Delphi
TListBox has a neat virtual mode), which is a bit of a bummer. Perhaps
you can extend it to make it virtual.

A virtual listbox has a writable "Count" property which determines how
many items are in it, and a "GetItem" event which gets the item at a
given index. In this way, the listbox adjusts its scrollbar according to
the height of each item times the Count, and paints only the visible
items, getting the items by calling GetItem. Requests through
ListBox.Items would call through to invoking the GetItem event.

The listbox is a very simple type of control (although getting all the
accessibility features just right could be more difficult, but I doubt a
speech synthesizer is going to have to list off all the items inside :),
so it could be reimplemented if necessary to get the right semantics.
You'd need to be aware of internationaliz ation and bidi text etc. too.

-- Barry

--
http://barrkel.blogspot.com/
Jun 9 '06 #7
My experience is that a lot of the GUI slows down the real data
processing of your application.
Suppose that you have a combobox which is connected to an ArrayList as
datasource, each time you add an object to the ArrayList, the GUI is
updated (the item apears in the combobox).

If you want to load a massive amount of data into your datasource and
display it on screen, you should avoid to have the GUI refresh itself
after each addition. I had the same problem and all I did was a
..SuspendLayout () call on the GUI element before the additions and a
..ResumeLayout( ) after the addition had finished.

But as I'm writing this, I took a glimpse at the ListBox class and
noticed the BeginUpdate() and EndUpdate() methods which would probably
do exactly what you want:

This snippet is taken from the Visual Studio Help:
ms-help://MS.VSCC.v80/MS.MSDN.v80/MS.NETDEVFX.v20 .en/CPref17/html/M_System_Window s_Forms_ListBox _BeginUpdate.ht m

public void AddToMyListBox( )
{
// Stop the ListBox from drawing while items are added.
listBox1.BeginU pdate();

// Loop through and add five thousand new items.
for(int x = 1; x < 5000; x++)
{
listBox1.Items. Add("Item " + x.ToString());
}
// End the update process and force a repaint of the ListBox.
listBox1.EndUpd ate();
}

Jun 9 '06 #8
<jo*****@yamaga ta-europe.com> wrote in message
news:11******** **************@ y43g2000cwc.goo glegroups.com.. .
But as I'm writing this, I took a glimpse at the ListBox class and
noticed the BeginUpdate() and EndUpdate() methods which would probably
do exactly what you want:


The OP is already using those methods - unsurprisingly, they're not
helping... :-)
Jun 9 '06 #9
> I don't think you're going about this the right way at all. I'd try and
make a user interface somewhat similar to the old index lookup in
WinHlp32.exe - as you type a value in, it zooms in on the location. If
the contents must be presented as a listbox, then make the listbox
virtual, so that only the visible elements are actually loaded. It
doesn't look like the .NET listbox can be made virtual (the Delphi
TListBox has a neat virtual mode), which is a bit of a bummer. Perhaps
you can extend it to make it virtual.


Yeah, I think virtual lists may be exactly what you need. I've used them
back in C++/MFC, have not tried yet in .NET though. A quick google search
for "c# virtual listbox" turned up:
http://www.vbaccelerator.com/home/ne...ox/article.asp

--
Adam Clauss
Jun 9 '06 #10

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