C# Discussion Boards - CodeProject

19-Nov-09 4:34

I have a Windows app and need to display large amounts of capture data in real-time. The .net listview control's virtual mode works, but each time I add a new item the whole control repaints. Any code out there that will do the trick. Thanks

Saksida Bojan19-Nov-09 5:00

19-Nov-09 5:00

http://bytes.com/topic/net/answers/790103-c-winform-prevent-listview-repainting[^]

There I saw one post that uses PInvoke: LockWindowUpdate
Scrool down a bit. It is the Fifth reply

Vincent Roggero19-Nov-09 6:19

19-Nov-09 6:19

I've tried this. It dosen't help when the ListView is in VirtualMode. Thanks

Luc Pattyn19-Nov-09 5:05

Luc Pattyn

19-Nov-09 5:05

if you want the new items to become visible right away, then the LV (or whatever other control you use) has to repaint itself, what else could it do?

if you don't want immediate display, you could collect new items outside the control, then add them to the control once either one of the following occurs: your new items in hand exceed a certain number, or some timeout has elapsed. The list-oriented controls have an AddRange method to do that efficiently.

I know of no control that would do all that automatically; of course you can derive your own from any of the existing list-oriented controls.

Smile | :)

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Vincent Roggero19-Nov-09 6:21

19-Nov-09 6:21

I want immediate displaying of the items, but don't want the control to repaint the whole view each time a VirtualItem is added. Thanks

Saksida Bojan19-Nov-09 6:36

19-Nov-09 6:36

so in other Word, you want to add an item, without losing viewing position (Scroll bar).

Have you tried Binding data source?

Vincent Roggero19-Nov-09 6:46

19-Nov-09 6:46

Not really. Think of this app as a protocol analyzer. As data is read it appears as a listview item. The current item is visible. I can make this work with the listview in non-virtualmode, but due to the fact that there is a large number of items being added to the listview, performance starts to go downhill fast. Putting the listview in virtualmode allows the listview to only maintain items within view. This also works fine if your adding all the items at once. In this case the listview calls me only when it needs to display an item during scrolling etc. The problem is when I change the VirtualCount to indicate that a new item is available the listview repaints the whole view. So what I get is a constant repainting of the view while new items are being added.

Saksida Bojan19-Nov-09 7:00

19-Nov-09 7:00

thanks for explanation. Now I Clearly know what it does.
Have you tried enabling DoubleBuffer?

If that won't work, then you need to override event: OnPaint and you handle it

Vincent Roggero20-Nov-09 4:08

20-Nov-09 4:08

I don't see where to enable DoubleBuffer.

Saksida Bojan20-Nov-09 5:06

20-Nov-09 5:06

There are several Articles on how to create ListView Flicker free.

Flicker-free ListView in .NET and XP[^]
Flicker-free ListView in .NET - Part 2[^]
http://msdn.microsoft.com/en-us/library/system.windows.forms.listview.doublebuffered.aspx[^]

At the button, there is an example how to enable DoubleBuffered without creating new class

Vincent Roggero20-Nov-09 7:02