467,075 Members | 962 Online
Bytes | Developer Community
Ask Question

Home New Posts Topics Members FAQ

Post your question to a community of 467,075 developers. It's quick & easy.

Progress bar update from worker thread

Hello all

Yes I know its been done before, but something silly is killing me on
this.

I have the standard progress bar and worker thread scenario with
progress of the worker thread being fed back to the main UI and
displayed on the progress bar. I have a delegate and am using
BeginInvoke. But the progress bar is not updating.

I have simplified my code below(and also built and tested this code).
Basic form1 with progress bar and button nothing else.
--------------------------------------------------------------------------------------------
Imports System
Imports System.Collections.Generic
Imports System.Text
Imports System.Threading
Imports System.IO
Public Class Form1

Dim worker As System.Threading.Thread ' Thread
Dim worker_obj As New worker_class ' Object from
worker class
Public Sub New()
Me.InitializeComponent()
'ProgressBar1
ProgressBar1.Name = "ProgressBar1"
ProgressBar1.Maximum = 100
ProgressBar1.Value = 10
End Sub

Sub UpdateProgressDisplay(ByVal Value_for_progress_bar As Integer)
ProgressBar1.Value = Value_for_progress_bar
Application.DoEvents()
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e
As System.EventArgs) Handles Button1.Click

worker = New Thread(AddressOf
worker_obj.DoRemoteCommunications)

' Now actually start the comms thread.
worker.Start()
End Sub
End Class

Public Class worker_class

' Set up delegate for assync function call.
--------------------------------
Public Delegate Sub Async_Update_Progress_caller(ByVal
Value_for_progress_bar As Integer)
Public Sub DoRemoteCommunications()
Console.WriteLine("Comms worker thread started.....")

' Set up delegate to allow asynchronous calls between threads.
Dim caller As New Async_Update_Progress_caller(AddressOf
Form1.UpdateProgressDisplay)

' Initiate the asynchronous call.
Dim result As IAsyncResult

result = caller.BeginInvoke(100, Nothing, Nothing)
Console.WriteLine("Progress value 25 passed ")
Thread.Sleep(3000)
Console.WriteLine("Comms worker thread Finished.")

End Sub

End Class

--------------------------------------------------------------------------------------------
Many thanks for any help.

Denis
_______________________
http://www.CentronSolutions.com
Dec 4 '07 #1
  • viewed: 1726
Share:
4 Replies
>I have the standard progress bar and worker thread scenario with
>progress of the worker thread being fed back to the main UI and
displayed on the progress bar. I have a delegate and am using
BeginInvoke. But the progress bar is not updating.
You should use Control.BeginInvoke on a control or form, not
Delegate.BeginInvoke.

Mattias

--
Mattias Sjögren [C# MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.
Dec 4 '07 #2
Hi Mattias

Thanks for your help.

Ok Im not familiar with control.begininvoke.

Ive changed the worker class as below using

Form1.ProgressBar1.BeginInvoke(caller)

Now Im getting the following run time error.
"Invoke or BeginInvoke cannot be called on a control until the window
handle has been created."

But Form1.ProgressBar1 is on the form. Im confused.

--------------------------------------------------------------------------------------------------

Public Class worker_class

' Set up delegate for assync function call.
--------------------------------
Public Delegate Sub Async_Update_Progress_caller(ByVal
Value_for_progress_bar As Integer)
Public Sub DoRemoteCommunications()
Console.WriteLine("Comms worker thread started.....")

' Set up delegate to allow asynchronous calls between threads.
Dim caller As New Async_Update_Progress_caller(AddressOf
Form1.UpdateProgressDisplay)

' Initiate the asynchronous call.
Dim result As IAsyncResult

result = Form1.ProgressBar1.BeginInvoke(caller)
Console.WriteLine("Progress value 25 passed ")
Thread.Sleep(3000)
Console.WriteLine("Comms worker thread Finished.")

End Sub

End Class
----------------------------------------------------------------------------------------------------------

Thanks for your help

Denis
On Dec 4, 9:45 pm, Mattias Sjögren <mattias.dont.want.s...@mvps.org>
wrote:
I have the standardprogressbarandworkerthreadscenario with
progressof theworkerthreadbeing fed back to the main UI and
displayed on theprogressbar. I have a delegate and am using
BeginInvoke. But theprogressbaris not updating.

You should use Control.BeginInvoke on a control or form, not
Delegate.BeginInvoke.

Mattias

--
Mattias Sjögren [C# MVP] mattias @ mvps.orghttp://www.msjogren.net/dotnet/|http://www.dotnetinterop.com
Please reply only to the newsgroup.
Dec 5 '07 #3
Mattias Sjögren wrote:
>I have the standard progress bar and worker thread scenario with
progress of the worker thread being fed back to the main UI and
displayed on the progress bar. I have a delegate and am using
BeginInvoke. But the progress bar is not updating.
Have you come across the BackgroundWorker class yet? (new to Framework
2.0, IIRC). It is specifically designed for this situation, marshaling
events from the worker thread back onto the UI thread and getting round
all these marshaling problems.

HTH,
Phill W.
Dec 5 '07 #4
I've not really mucked around with threads much, but why not just use
..DoEvents within the processing loop?

-SurturZ

"Phill W." wrote:
Mattias Sjögren wrote:
I have the standard progress bar and worker thread scenario with
progress of the worker thread being fed back to the main UI and
displayed on the progress bar. I have a delegate and am using
BeginInvoke. But the progress bar is not updating.

Have you come across the BackgroundWorker class yet? (new to Framework
2.0, IIRC). It is specifically designed for this situation, marshaling
events from the worker thread back onto the UI thread and getting round
all these marshaling problems.

HTH,
Phill W.
Dec 6 '07 #5

This discussion thread is closed

Replies have been disabled for this discussion.

Similar topics

5 posts views Thread by Søren Reinke | last post: by
5 posts views Thread by Tomaz Koritnik | last post: by
8 posts views Thread by WhiteWizard | last post: by
4 posts views Thread by Joachim | last post: by
5 posts views Thread by dgleeson3@eircom.net | last post: by
10 posts views Thread by =?Utf-8?B?YXVsZGg=?= | last post: by
By using this site, you agree to our Privacy Policy and Terms of Use.