Hi,
I'm having a problem with my app. All its supposed to do is put the word
"Check" in a listbox every 2 seconds!
I'm getting a System.InvalidO perationExcepti on error, more specifically,
"Cross-thread operation not valid: Control 'ListBox1' accessed from a thread
other than the thread it was created on."
Please help! Here's my code...
Thanks, Paul
Imports System
Imports System.Timers
Public Class Form1
Dim mytimer As New System.Timers.T imer()
Private Sub btnStart_Click( ByVal sender As System.Object, ByVal e As
System.EventArg s) Handles btnStart.Click
AddHandler mytimer.Elapsed , AddressOf OnTimedEvent
mytimer.Interva l = 2000
mytimer.Enabled = True
mytimer.Start()
End Sub
Private Sub btnStop_Click(B yVal sender As System.Object, ByVal e As
System.EventArg s) Handles btnStop.Click
mytimer.Enabled = False
mytimer.Stop()
End Sub
Private Sub OnTimedEvent(By Val source As Object, ByVal e As
ElapsedEventArg s)
'My.Computer.Fi leSystem.WriteA llText("C:\test .log", "test", True)
ListBox1.Items. Add("Check..." & Date.Now())
End Sub
End Class
7  8155 
>Dim mytimer As New System.Timers.T imer()
The easiest solution would be to use a System.Windows. Forms.Timer
instead of the System.Timers.T imer.
Mattias
--
Mattias Sjögren [C# MVP] mattias @ mvps.org http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.
Ok, I made that change, and changed the AddHandler mytimer.Elapsed ,
AddressOf OnTimedEvent line to read
AddHandler mytimer.Tick, AddressOf OnTimedEvent as VB said I should but now
I get this error on the same line...
hanged
"Mattias Sjögren" <ma************ ********@mvps.o rgwrote in message
news:%2******** ********@TK2MSF TNGP06.phx.gbl. ..
Dim mytimer As New System.Timers.T imer()
The easiest solution would be to use a System.Windows. Forms.Timer
instead of the System.Timers.T imer.
Mattias
--
Mattias Sjögren [C# MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.
Oops it would help to include the error!
Method 'Private Sub OnTimedEvent(so urce As Object, e As
System.Timers.E lapsedEventArgs )'
does not have the same signature as delegate 'Delegate Sub
EventHandler(se nder As Object,
e As System.EventArg s)'
Thanks,
Paul
"Paul" <ia*@home.co.uk wrote in message
news:t4******** *************@p ipex.net...
Ok, I made that change, and changed the AddHandler mytimer.Elapsed ,
AddressOf OnTimedEvent line to read
AddHandler mytimer.Tick, AddressOf OnTimedEvent as VB said I should but
now I get this error on the same line...
hanged
"Mattias Sjögren" <ma************ ********@mvps.o rgwrote in message
news:%2******** ********@TK2MSF TNGP06.phx.gbl. ..
>Dim mytimer As New System.Timers.T imer()
The easiest solution would be to use a System.Windows. Forms.Timer
instead of the System.Timers.T imer.
Mattias
--
Mattias Sjögren [C# MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.
"Paul" <ia*@home.co.uk wrote in
news:Qd******** *************** *******@pipex.n et:
I'm having a problem with my app. All its supposed to do is put the
word "Check" in a listbox every 2 seconds!
I'm getting a System.InvalidO perationExcepti on error, more
specifically, "Cross-thread operation not valid: Control 'ListBox1'
accessed from a thread other than the thread it was created on."
WIndows forms are single threaded - you need to use use Control.BeginIn voke
to marshal the call back to the proper thread.
Do a google search and you'll find plenty of examples.
Sorry, I've fixed it.
I wasn't using Timer1_Tick!
Using that instead of the OnTimedEvent sub now.
Private Sub Timer1_Tick(ByV al sender As Object, ByVal e As System.EventArg s)
Handles Timer1.Tick
ListBox1.Items. Add("Check..." & Date.Now())
Cheers!
Paul
"Paul" <ia*@home.co.uk wrote in message
news:t4******** *************@p ipex.net...
Ok, I made that change, and changed the AddHandler mytimer.Elapsed ,
AddressOf OnTimedEvent line to read
AddHandler mytimer.Tick, AddressOf OnTimedEvent as VB said I should but
now I get this error on the same line...
hanged
"Mattias Sjögren" <ma************ ********@mvps.o rgwrote in message
news:%2******** ********@TK2MSF TNGP06.phx.gbl. ..
>Dim mytimer As New System.Timers.T imer()
The easiest solution would be to use a System.Windows. Forms.Timer
instead of the System.Timers.T imer.
Mattias
--
Mattias Sjögren [C# MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.
"Spam Catcher" <sp**********@r ogers.comschrie b:
>I'm having a problem with my app. All its supposed to do is put the
word "Check" in a listbox every 2 seconds!
I'm getting a System.InvalidO perationExcepti on error, more
specifically , "Cross-thread operation not valid: Control 'ListBox1'
accessed from a thread other than the thread it was created on."
WIndows forms are single threaded - you need to use use
Control.BeginIn voke
to marshal the call back to the proper thread.
Do a google search and you'll find plenty of examples.
Articles and resources on the topic:
Multithreading in Windows Forms applications
<URL:http://dotnet.mvps.org/dotnet/faqs/?id=multithread ing&lang=en>
--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://dotnet.mvps.org/dotnet/faqs/>
Paul wrote:
Hi,
I'm having a problem with my app. All its supposed to do is put the word
"Check" in a listbox every 2 seconds!
I'm getting a System.InvalidO perationExcepti on error, more specifically,
"Cross-thread operation not valid: Control 'ListBox1' accessed from a thread
other than the thread it was created on."
You'll need to do a couple of steps:
1) Create an AddItemToList sub
2) define a delegate
3) create a delegate
4) check if the list needs to invoke before adding the item in the list
1)
Sub AddItemtoList(S as String)
lst.Items.Add(S )
end sub
2)
Private delegate sub _AddItem(S as String)
3)
Private AddItemDel as _AddItem
....
Sub New()
....
AddItemDel = new _AddItem(Addres sof AddItemToList)
....
end sub
4)
.....
Sub Somesub
if lst.invokerequi red then
lst.invoke(AddI temDel, StringToAdd)
else
AddItemToList(S tringToAdd)
end if
end sub
Using this you'll be able to call Somesub from withen your thread proc
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