ListView taking a long time to select.

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Guest

I have a ListView that I am showing in 'Detail' mode. The list contains about 740 items and I have a button that tries to go through all items in the list and select them and change the image icon. This seems to take over a minute or two just to do something like

foreach(ListViewItem item in listView.Items

item.Selected = true
item.ImageIndex = 1


Does anyone have any suggestions on how to speed this up? I would hate to guess how long it would take if I had 7000 items in the list. What is taking so long? I have tried to suspend the layout as is done during the Windows initialization but this did not seem to have any effect

Thank you for your suggestions

Kevin
 
* =?Utf-8?B?S2V2aW4gQnVydG9u?= said:
I have a ListView that I am showing in 'Detail' mode. The list
contains about 740 items and I have a button that tries to go through
all items in the list and select them and change the image icon. This
seems to take over a minute or two just to do something like:

foreach(ListViewItem item in listView.Items)
{
item.Selected = true;
item.ImageIndex = 1;
}

Does anyone have any suggestions on how to speed this up? I would hate
to guess how long it would take if I had 7000 items in the list. What is
taking so long? I have tried to suspend the layout as is done during the
Windows initialization but this did not seem to have any effect.
Click to expand...

Have a look at the control's 'BeginUpdate' and 'EndUpdate' methods.
'SuspendLayout' doesn't have any influence in this case because no
layouting (repositioning of controls) is done.
 
Thank you for your suggestion. But this did not help. The exact code that I am executing is

cardholderList.BeginUpdate()
resetProgressBar.Minimum = 0
resetProgressBar.Maximum = cardholderList.Items.Count
resetProgressBar.Step = 1
resetProgressBar.Value = 0
foreach(ListViewItem item in cardholderList.Items

item.Selected = true
item.ImageIndex = 1
resetProgressBar.PerformStep()

cardholderList.EndUpdate()

I have tried it with and without the progress bar. It seems to take equally long

Kevi

----- Herfried K. Wagner [MVP] wrote: ----

* =?Utf-8?B?S2V2aW4gQnVydG9u?= said:
I have a ListView that I am showing in 'Detail' mode. The lis
contains about 740 items and I have a button that tries to go throug
all items in the list and select them and change the image icon. Thi
seems to take over a minute or two just to do something like

item.Selected = true
item.ImageIndex = 1

to guess how long it would take if I had 7000 items in the list. What i
taking so long? I have tried to suspend the layout as is done during th
Windows initialization but this did not seem to have any effect
Click to expand...

Have a look at the control's 'BeginUpdate' and 'EndUpdate' methods
'SuspendLayout' doesn't have any influence in this case because n
layouting (repositioning of controls) is done
 
As an update I ran the code through a profiler and found that setting the 'Selected' to true (item.Selected = true) was taking 98% of the time. There seems to be alot of overhead with this call. Is there a faster way of setting an item 'Selected'

Kevi

cardholderList.BeginUpdate()
resetProgressBar.Minimum = 0
resetProgressBar.Maximum = cardholderList.Items.Count
resetProgressBar.Step = 1
resetProgressBar.Value = 0
foreach(ListViewItem item in cardholderList.Items

item.Selected = true
item.ImageIndex = 1
resetProgressBar.PerformStep()

cardholderList.EndUpdate()
 
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