Listview

  • Thread starter Thread starter Ken
  • Start date Start date
K

Ken

I have a listview with 24 rows and 150 columns. I update 3 rows every 10
seconds.

1 2 3 4 ... 150
row1
row2
row3
row4
..
..
..
row24

When this update occurs, I get a processor "spike" of 100% for a total of 7
seconds each update. This "spike" appears to use all of the processor which
is having adverse effects on other threads in the application (losing data,
failed communications, etc..).

I wrote example listviews in Visual C++ 6, Visual Basic 6, and VB .NET. Each
listview performed the same task - update 3 rows every ten seconds.

C++ and VB 6: There was a very small bump in processor usage - around 10% -
12%.
VB .NET: There was a spike of 60% - 70%.

It appears that updating a listview - in VB .NET - can be very expensive.

Has anyone else noticed this problem?
Is there a way to present the data this way without causing the processor
"spike" in VB .NET?
Why is there such a big difference between C++6,VB6, and VB .NET?

Thanks for your help.

K
 
Have you tried turning off the painting until all three rows are
updated?

listviewName.BeginUpdate()
Do your updating here
listviewName.EndUpdate()

Shane
 
Ken,

Can you tell us how long processing of this code takes.

Just a new project a listview on it and than this in the loadevent

\\\
ListView1.View = View.Details
For i As Integer = 1 To 150
ListView1.Columns.Add(i.ToString, 40, HorizontalAlignment.Left)
Next
Dim start As Integer = Environment.TickCount
ListView1.BeginUpdate()
For j As Integer = 1 To 24
ListView1.Items.Add(j.ToString)
For i As Integer = 1 To 150
ListView1.Items(j - 1).SubItems.Add(i.ToString)
Next
Next
ListView1.EndUpdate()
MessageBox.Show((Environment.TickCount - start).ToString & "Ms")
///

I hope this helps,

Cor
 
Thanks.

Yes, I tried it and it gives a wicked flicker of the entire list control.
No (good) change in processor usage.
 
Thanks. The test I conducted with the code below takes approx 120
milliseconds.

I have added something to the code that makes it more or less a mirror of
what I am doing. It is listed below. It takes much more time. Any major
problems with it that you can see?

Added a timer and set the interval to 10000 ms.
Inside the timer method:

Dim start As Integer = Environment.TickCount
ListView1.BeginUpdate()
For j As Integer = 1 To 24
For i As Integer = 1 To 150
ListView1.Items(j - 1).SubItems(i).Text = i.ToString
Next
Next
ListView1.EndUpdate()
MessageBox.Show((Environment.TickCount - start).ToString & "Ms")
Click to expand...

I also changed your code snippet to add all 0's upon startup. This is how my
app currently functions.
 
I have been testing your scenario some more. I have come up with a 70-80
millisecond time when loading. Just a FYI. 120 to 80 Ms is a big difference.
 
Just curious,
Are you doing this as a client app or as a web app with a server side
control?
 
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