memory issuse with listview control?

  • Thread starter Thread starter Michael M.
  • Start date Start date
M

Michael M.

HI all,

When I add items to a Listview control, then clearing the items and adding
more items my program seems to allocate a few KB of data and then not free
the Memory. I noticed this about half way through writing a program and
it's driving me a bit mad. I have posted a sub function below that I used
to test this problem:

The Sub is called every 4 seconds by a timer object, every 4 the seconds the
memory usage of the program is incremented by arround 40K. if I leave it
running for 20 minutes it can get as large as 50 megabytes.

Test setup:
VB.net 2005 Express, with .net framework 2 on XP Pro service pack 2.
P4 CPU arround 3 Ghz
1 GIG of DDR memory.
Sub AddProcessData()

ListView1.items.clear()

For Each oProcess As Process In Diagnostics.Process.GetProcesses

Dim lv As New ListViewItem

Try

lv.Text = oProcess.MainModule.ModuleName

lv.SubItems.Add(oProcess.Id.ToString)

lv.SubItems.Add(oProcess.StartTime.ToString)

ListView1.Items.Add(lv)

Catch ex As Exception

End Try

lv = Nothing

oProcess = Nothing

Next

End Sub

Anyone know what's happening here? calling GC.Collect does not help either.

I am new to .net programming so there is a good chance I am overlooking
something obvious

Regards,

Mike.
 
No worries,

I figured it out, and intresting that the application now starts out bieng
quite large in memory then gets smaller and smaller, I guessing that alot of
the objects used at the start of the application are eventually being freed
by the garbage collector thing.

the program now peaks at around 19 MB, then drops to about 9 MB over time
that I think people can live with.

Another thing with the Listview though class erases the background of the
controll before building the new list; this makes the ListView Flicker when
you are updating the information on a regular basis I found some code in C#
that exampled subclassing a textbox and making sure it was only numeric
input by discarding the window's messagess; I adapted it to VB and made it
discard wm_erasebackground

When I am updating the listbox I set the blnUpdatingControl = true from the
form class code; this prevents it from flickering.


Public Class CLS_SC_listview

Inherits ListView

Public blnUpdatingControl As Boolean = False

Private Const WM_ERASEBKGND = &H14

Protected Overrides Sub WndProc(ByRef message As
System.Windows.Forms.Message)

If message.HWnd = MyBase.Handle Then

Select Case message.Msg

Case WM_ERASEBKGND

If blnUpdatingControl = True Then

' Ignore paint message

Else

MyBase.WndProc(message)

End If

Case Else




MyBase.WndProc(message)

End Select

Else

MyBase.WndProc(message)

End If

End Sub

End Class

Regards,

Mike.

PS does anyone have good resources on using the system.runtime interop and
Marshalling.
 
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