Listview ....very SLOW when adding items

Hello,

I´m adding maybe 2-500 items into a Listview and its very slow...
Anyone know a resolutiion to this problem....

My code is very plain just a For loop which adds items while the recordset is not EOF ... so i don´t really know what could be wrong ....

Thanks in advance
vanki

Hi vanki :D

How about popping a copy of your code here for us to take a look at.

The problem might be that every time you add an item, the listview redraws itself, which can take a while. Before the loop, call the listview's beginUpdate() method and after the loop call its EndUpdate() method.

For Each oResult In oSearch.SearchResults
System.Windows.Forms.Application.DoEvents()
lstvResults.BeginUpdate()
If bStop = True Then
Exit For
End If
Dim itmX As New ListViewItem()
Dim s As Integer
If oCols.Item(0).Name = "Size" Then
itmX.Text = CInt(oResult.Fields.Item(oCols.Item(0).Name).Value / 1024) & "KB"
Else
itmX.Text = CStr(oResult.Fields.Item(oCols.Item(0).Name).Value)
End If

itmX.Tag = oResult.DocumentID

If oResult.Extension = ".msg" Then
itmX.ImageIndex = 10
ElseIf oResult.Extension = ".doc" Then
itmX.ImageIndex = 8
ElseIf oResult.Extension = ".xls" Then
itmX.ImageIndex = 9
ElseIf oResult.Extension = ".ppt" Then
itmX.ImageIndex = 18
ElseIf oResult.Extension = ".mdb" Then
itmX.ImageIndex = 20
ElseIf oResult.Extension = ".gif" Or oResult.Extension = ".jpg" Or oResult.Extension = ".tif" Or oResult.Extension = ".bmp" Then
itmX.ImageIndex = 22
ElseIf oResult.Extension = ".pdf" Then
itmX.ImageIndex = 24
Else
itmX.ImageIndex = 13
End If
If oCols.Count() = 1 Or oCols.Count > 1 Then
For s = 1 To oCols.Count - 1
If oCols.Item(s).Name = "Size" Then
itmX.SubItems.Add(CInt(oResult.Fields.Item(oCols.Item(s).Name).Value / 1024) & "KB")
Else
itmX.SubItems.Add(CStr(oResult.Fields.Item(oCols.Item(s).Name).Value))
End If

Next
End If

lstvResults.Items.Add(itmX)

lstvResults.EndUpdate()
prgrBar.PerformStep()

counter = counter + 1

Next

I agree with DSAINMON and I think the beginupdate and endupdate is good to check, but you have to keep it outside the loop, not inside as you are now. Now you are calling the methods for every round of the loop, saving nothing.

I tried the BeginUpdate and EndUpdate and put it ouside of the for loop but it makes no difference ....

You should also remove the DoEvents which will slow it down a lot.

VB Code:

[b]lstvResults.BeginUpdate()[/b]
 
For Each oResult In oSearch.SearchResults
[b]'System.Windows.Forms.Application.DoEvents()[/b]
If bStop = True Then 
Exit For 
End If 
Dim itmX As New ListViewItem() 
Dim s As Integer 
If oCols.Item(0).Name = "Size" Then 
itmX.Text = CInt(oResult.Fields.Item(oCols.Item(0).Name).Value / 1024) & "KB" 
Else 
itmX.Text = CStr(oResult.Fields.Item(oCols.Item(0).Name).Value) 
End If 
 
itmX.Tag = oResult.DocumentID 
 
If oResult.Extension = ".msg" Then 
itmX.ImageIndex = 10 
ElseIf oResult.Extension = ".doc" Then 
itmX.ImageIndex = 8 
ElseIf oResult.Extension = ".xls" Then 
itmX.ImageIndex = 9 
ElseIf oResult.Extension = ".ppt" Then 
itmX.ImageIndex = 18 
ElseIf oResult.Extension = ".mdb" Then 
itmX.ImageIndex = 20 
ElseIf oResult.Extension = ".gif" Or oResult.Extension = ".jpg" Or oResult.Extension = ".tif" Or oResult.Extension = ".bmp" Then 
itmX.ImageIndex = 22 
ElseIf oResult.Extension = ".pdf" Then 
itmX.ImageIndex = 24 
Else 
itmX.ImageIndex = 13 
End If 
If oCols.Count() = 1 Or oCols.Count > 1 Then 
For s = 1 To oCols.Count - 1 
If oCols.Item(s).Name = "Size" Then 
itmX.SubItems.Add(CInt(oResult.Fields.Item(oCols.Item(s).Name).Value / 1024) & "KB") 
Else 
itmX.SubItems.Add(CStr(oResult.Fields.Item(oCols.Item(s).Name).Value)) 
End If 
 
Next 
End If 
 
lstvResults.Items.Add(itmX) 
prgrBar.PerformStep() 
 
counter = counter + 1 
 
Next
[b]lstvResults.EndUpdate()[/b]

I need the DoEvents so the user can stop the process

I think you may be stuck with it being slow then, especially if its 500 items. Or maybe only do events on every third item or every 5 items or something. See DoEvents has to check and let all other system processes run so it is checking on EVERY item and slowing you down.

I tried to comment out the DoEvents .... but the speed doesnt change at all