Waiting For Threads - Thread.join Suspend Execution Of Code On Calling Thread Until Spawned Thread Finishes Or Is Aborted
Sep 2, 2010
My understanding is that thread.join will suspend the execution of code on the calling thread until the spawned thread finishes or is aborted...
With that in mind, I tried this:
For i = 1 to 50
threads = New Thread(AddressOf test)
threads.IsBackground = True
threads.SetApartmentState(ApartmentState.STA)
[CODE]...
However, the rest of the code runs when the loop finishes, not waiting for all the spawned threads to finish. Since the rest of the code needs the threads to finish (otherwise the rest will error).
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Jul 1, 2011
I am trying to use a separate thread to handle specific events in VB.Net. The idea being that I do not want the main application to be held up if a particular event handler takes awhile to finish. How do I get my main thread loop to suspend the thread while allowing it to handle events when they occur?When I create a Windows Forms application, there is a UI thread that handles the UI events. I do not imagine that this thread is continuously polling some variable to see if someone has pressed a button. I imagine the thread is suspended until the OS tells it there is something to do. I was trying to figure out how to ensure that my event handlers were not being executed by the UI thread. From what I have read, I can do this by raising the events from a different thread. But what does that thread do while it is waiting for other events, just exit?
I wanted to know how to create a thread that works like the UI thread, only it processes the events I want it to process. I am not sure how events work in .Net. I understand that event handlers are run on the thread that raises the event. I believe that .Net allocates threads from some thread pool to process events such as timer events. I am not clear on how it works, though, and what those threads are doing when they are not handling events.
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Dec 31, 2010
Is it possible to wait/suspend execution for a certain amout of time without hanging the main UI thread?
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Nov 9, 2011
in my Winforms application, there is a main thread. It is not the UI thread but it starts the UI thread. In the main thread, I'm using a Mutex to prevent the application from being started twice. That's why I'm making an exception from the rule not to use a Thread's Join method. In this case, the main thread does call UIThread.Join before releasing the Mutex. That works well.
The strange problem is: Whenever an exception occurs in the UI thread, the default Windows error dialog pops (send report, debug, close). If I select "close", the application does not quit. Instead, the main window (created in the UI thread) stays visible, but it is inoperatable. It looks as if the UI thread still does not quit, and consequently the main thread's call to UIThread.Join doesn't return either.
Though, if I debug the application at that point, the "threads" window does not show the UI thread anymore. I've given it the name "UI Thread" (surprisingly).So, why does the Join method not return even if the thread has died? Why is a window of a died thread visible?The following screenshot shows the Threads window below and the window above shows the callstack of the main thread ("Hauptthread").
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Aug 27, 2011
I am trying to call a method that started on a background thread on the UI thread calling BeginInvoke and passing in a delegate as follows:
Dispatcher.BeginInvoke(Function() UpdateApplicationDataUI())
to call this method:
Private Sub UpdateApplicationDataUI()
...
End Sub
However, I get an error in the call to BeginInvoke (the UpdateApplicationDataUI portion of the delegate is stating "Expression does not produce a value").
Me.Dispatcher.BeginInvoke(Function() New Action(AddressOf UpdateApplicationDataUI))
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Nov 25, 2011
I have am using a Twitter streaming class library, and would like to update a listbox when a new tweet is posted. I have it all set up to the point where a message box will show when a tweet comes in, but when I try to insert this tweet into a listbox I get this error: The calling thread cannot access this object because a different thread owns it. I don't know what I need to do in order to insert this tweet.
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Oct 31, 2010
My routine to check for updates is run as a separate process. Exiting the application is required to update, so a dialog asks the user, when an update is found, if they want to exit now. f they do, the code (from the update thread) calls Application.Exit().However, if the FormClosed event of any form that needs to be closed needs to access its controls, an invalid cross-thread operation is detected (which sounds pretty logical).
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Aug 13, 2010
In one application, I need use 4 simultaneous threads.When the threads finished, I need to update the text of a TextBox.So, I create 4 Textbox, and I wanna the threads change the text to FINISHED.Each thread change one distinct TB.I use this "example"
Dim Terminados As Integer = 0
Private Sub frmEnviarMensagem_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Timer1.Enabled = True
Timer1.Start()
[code]....
The problem is, I have an error in the red lines.The error is: INVALIDOPERATIONEXCEPTION "Cross-Thread operation not valid: Control tbPlaca1 Accessed from a thread other than the thread it was created on."I don't use cross threading. Each TB only was accessed for the correspondent thread, and for the "main program".
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Nov 3, 2011
This is the error message I am getting:
"Cross-thread operation not valid: Control 'Panel1' accessed from a thread other than the thread it was created on." The reason I am getting this error is because I am opening up a new form and then calling these three things:
Panel1.Show()
Label1.Show()
Label2.Show()
why I get this error message because it doesn't occur normally if I open Form2 after closing Form1, it only occurs when I open Form2 after closing Form4.
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Jul 21, 2009
I have done a program using vb2005 to display reading from my microcontroller bs2 board but have encountered some problems. My code are as follows.
Dim Stop_Rx As Boolean
Private Sub btnRead_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnRead.Click
SerialPort1.Open()
[code]....
I've encounter an error which is, (Cross-thread operation not valid: Control 'txt1' accessed from a thread other than the thread it was created on.)
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Jun 21, 2012
When my client try to connect to server I'm getting this error : Cross-thread operation not valid: Control 'l_users' accessed from a thread other than the thread it was created on.
Private Sub _socketManager_onConnectionAccept(ByVal SocketID As String) Handles _socketManager.onConnectionAccept
l_Users.Items.Add(SocketID)
End Sub
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Feb 17, 2012
Would anyone be able to help me here please. I'm fairly new to VB.net and threading so im just trying to figure out what is happening.When I debug this I am getting the error thread operation not valid: Control 'ProgressBar1' accessed from a thread other than the thread it was created on.
I'm a little lost as to why the error is occuring or how to fix it. I've had to put the progress bar in a separate thread otherwise the GUI crashes
[Code]...
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Jun 6, 2010
I have written an application that loads a form - frmCad as well as AutoCad. It does this via a class which detects when AutoCad quits.
Friend Class CadApp Private WithEvents AppObject As AcadApplication... Private Sub AppObject_BeginQuit(ByRef Cancel As Boolean) Handles AppObject.BeginQuit RaiseEvent Quit() End SubEnd Class
My main class loads frmCad as well as CadApp.
Public Class Cad Private WithEvents frmCad As CadForm Private WithEvents app As CadApp... Public Sub ShowForm() If frmCad Is Nothing Then frmCad = New CadForm frmCad.Visible = True End Sub... Private Sub app_Quit() Handles app.Quit frmCad.Dispose() frmCad = Nothing .... End Sub
When I debug the program, it stops at frmCad.Dispose()The program continues to execute, but all the code after it fails to work.Looking more carefully I get an error message which contains:-Cross-thread operation not valid: Control 'Autocad' accessed from a thread other than the thread it was created on.
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Feb 9, 2011
My error:Cross-thread operation not valid: Control 'label2' accessed from a thread other than the thread it was created on. I want to be able to give my Public RunBot() sub access to edit Labels, buttons, etc without an error.
[Code]...
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Apr 1, 2010
I'm getting the 'System.InvalidOperationException' error on acccessing a thread from other than where it was created. My code is:
'Required by the Windows Form Designer
Public components As System.ComponentModel.IContainer ' changed from private
[code]....
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Jun 6, 2009
My problem is Cross-thread operation not valid: Control 'statusHO' accessed from a thread other than the thread it was created on.
System.InvalidOperationException was unhandled
Message="Cross-thread operation not valid: Control 'statusHO' accessed from a thread other than the thread it was created on."
Source="System.Windows.Forms"
StackTrace:
[Code]...
i used it and it works fine then. but as it is mentioned its not a good practice to use it. So what should i do? is it ok if i use this as i am not able to use correct practice. Mine application is not for enterprise purpose. its just my class project, and it works fine even if i put application working in background. System works ok. I dont know how to correct this error.As i dont have that much knowlege of threads.
So please guide me how to fix this in correct way otherwise i am force to go for bad programming practice
Please refer to Windows Mobile Developer Center > Smart Device Development Forums > Windows Mobile Development > Appendtext not working for all my code details
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Aug 4, 2009
Cross-thread operation not valid: Control 'lv1' accessed from a thread other than the thread it was created on.
Dim lvi As ListViewItem
For Each lvi In lv1.Items
[code]....
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Feb 7, 2011
Ok i have a Form with the following
Private Sub frmMain_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
txtNotepad.Text = LoadFile("notes.txt")
[code].....
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Apr 22, 2011
I have an app in vb net 2005 which has code similar to' start external thread ShowRandom Images.start Open database & do other preliminary setup 'abort thread ShowRandom Images. abort 99 times out of 100 I never get a problem, but if system appears to be slow or other heavy processing, I get "Thread being aborted"..How can I trap or ensure the error message does not get to my users
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Jan 19, 2009
I am facing a problem while joining a STA thread to MTA thread. Actually the requirement was some thing like describe below.
1. I have a exe which is using some dialog boxes.
2. These dialog boxes are using MSFlexGrid. This component is a Com component.
3.so in order to run it with Vb.Net exe i had to run this dialog box in a STA thread.
4. to achive this i created a new thread and set the Apartment status STA.
5.it was working fine when i run the code. but if click on exe than at the time of join it throws an unhandled exception.if i click on continue button of exception dialog box it runs successfully. how ever i can not ignore this exception.
6. exception contains below text (i know its a bog message but i am stuck here for last couple of days.)[code]...
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Jul 8, 2011
I'm using the code below in a separate (background) thread, in order to read parts from a file, so they can be uploaded.
The problem is that when the user stops the upload, the thread is sometimes aborted while it's still reading from the file. This keeps the file locked and when the user starts the upload again, the following message appears.[code]...
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Jun 22, 2010
I have a a main thread and another background thread that does some work (see below).I want to do something within my worker thread and then wait until some other event happens in the main thread before continuing. How do I do this? I thought I could use ManualResetEvent but I can't get it to work properly. I'm a bit confused about the Set, Reset, WaitOne methods and where exactly I should call them from.When the worker thread is suspended it shouldn't affect the main thread.
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System. EventArgs) Handles MyBase.Load
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
[code]....
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Jan 11, 2010
I am using System.IO.Ports.SerialPort in my project. This is the first time I am using this component.
Let me explain the issue. My desktop is connected to a weigh scale where I am taking the readings through the COM port. In a particular function I need to give new settings (Baud, Parity, StopBits, DataBits) to the serialport. So I am closing the existing object, and opening it again with new settings.
I am getting "The I/O operation has been aborted because of either a thread exit or an application request." exception while closing the serial port. The code is follows
If frmMDI.SerialPortReader.IsOpen Then
frmMDI.SerialPortReader.Close() //Exception comes here
End If
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Jun 3, 2012
Looking for a solution to pause and resume a thread. When I use suspend and resume it says its no longer supported. Here is the code. I'm just trying to get it to cycle between two "do until" events.
[Code]...
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Mar 11, 2009
I am trying to make a marquee progress bar run while my long function is running. When the function is done running, I want the progress bar to disappear.
[code]...
If I don't do t.Join(), the progress bar disappears right away and then the thread runs. If I do Join(), the progress bar doesn't appear until the message box pops up after the thread is done!How would I get the effect of the progress bar running while the thread is running and then stopping when it's done?
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Sep 18, 2009
When i run the program i am getting the following error in this line TextBox1.Text &= "File Created: " & FullPath & vbCrLf"Cross-thread operation not valid: Control 'TextBox1' accessed from a thread other than the thread it was created on."
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Mar 4, 2009
I'm creating a Client Server application which involves theServer running some scripts in clients and getting back results in an automated way. In Server, other than Main thread, i have 2 worker threads, a) one monitoring response from clients and b) the other scheduling next available job to respective client which executes that job. The issue here is ,I want these worker threads to write the status of their work in the UI(which comes under Main Thread). Also i need to write things in worker thread in a Data table and Rich Text Box in Main thread. But, I can't do so, since it has been blocked to access one thread's function or property directly from others. Is there any work around to do this?
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Nov 12, 2009
Preface: I know this is an unusual/improper way to do this. I can do this with a "real" ShowDialog(), background worker/thread, and so on. I am trying to do specifically what I describe here, even if it is ugly. If this is impossible for X reason, I have created a fancy progress dialog for some of our long running operations. I need to have this dialog shown on a new thread while having processing continue on the calling (UI in most cases) thread.
[Code]...
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Sep 5, 2009
I need your help on the following. In debugging mode only the program is stopping to the following line "My.Forms.FormMain.HelpProviderMain.HelpNamespace = "Reports.chm"" with the following error ""An error occurred creating the form. See Exception.InnerException for details. The error is: Cross-thread operation not valid: Control 'FormSplash' accessed from a thread other than the thread it was created on.""
I noticed that when I am putting NONE in SPLASH screen option in the properties of the project, there is no problem.I am no familiar with treating that's why can you give me detail instruction how to overcome this annoying problem?
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Nov 14, 2009
I am getting this exception: Cross-thread operation not valid: Control 'TextBoxOutput' accessed from a thread other than the thread it was created on. in a VB 2008 Windows Forms application that I havent specifically made multi-threaded. I have create a sub called Out() like this:
Private Sub Out(ByVal inString As String)
Me.TextBoxOutput.Text += (Me.TextBoxOutput.Text & inString & vbNewLine)
Me.TextBoxOutput.SelectionStart = Me.TextBoxOutput.Text.Length
Me.TextBoxOutput.ScrollToCaret()
End Sub
and I call it from various events to log messages I am getting from my pbx, which I use a third party open source dll to access. The interesting thing to me is that if I run the deployed application (ie, not in the VS IDE) I do not get any exceptions, it's only from within the IDE.if I add the line: Control.CheckForIllegalCrossThreadCalls = False to the form's constructor, the exceptions stop, but a) this seems like a hacky way to get around the issue and b) the application seems to hang sometimes when I have it set this way.
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