ListView is extremely slow

[Teemu]

I have a listview which contains about 500 items. I was pretty confused when
I realized that it takes over 50 milliseconds to get
Listview.CheckedItems.Count value. How it can be so slow?

In ItemChecked event I have code which sets text "3 items selected" to a
label. When I turn CheckBoxes to True you can imagine how long it takes.

I'm using Visual Basic 2005.

Any good ideas?

Thanks,
Teemu

 

[Cerebrus]

Hi,

Virtual ListView seems the way to go.

There are many samples available. Don't know if they're available for
VS 2005.

Here's one that you can try :

http://www.windowsforms.com/ControlGallery/ControlDetail.aspx?Control=214&tabindex=9

Also, an MSDN article on how to create a Virtual Listview:

http://msdn.microsoft.com/downloads...samples/internet/commctrl/vlistvw/default.asp

Hope this helps,

Regards,

Cerebrus.

 

[Jason Newell]

Teemu,

I would give LVM_GETITEMCOUNT a try to see if it's any faster.

http://msdn.microsoft.com/library/d...mmctls/listview/messages/lvm_getitemcount.asp

Declare Function SendMessage Lib "User32.dll" (ByVal hWnd As IntPtr,
ByVal Msg As Integer, ByVal wParam As Integer, ByVal lParam As Integer)
As IntPtr

LVM_FIRST = 0x1000
LVM_GETITEMCOUNT = (LVM_FIRST + 4)

Jason Newell

 

[Claes Bergefall]

Not surprising actually. CheckedItems.Count actually loops over all items in
your list box and counts the ones that are checked.
How about keeping a counter yourself? Then you only need to add or subtract
1 in the ItemChecked event

/claes

 

[Jason Newell]

Totally sorry, I missed the "Checked" statement. I'll repost if I can
think something else up.

Jason Newell