Error On Worker Thread
Dec 27, 2009
I have some class that splits some work onto multiple worker threads. To be more specific: the class represents a download, that can have as many segments as the user wants, that get then put onto separate threads.When I run the download with one segment, it works fine. When I run it with 2 segments, the second segment encounters an error.[code]When I put a breakpoint on the if, it'll stop there, but when I go to the next line, I get an error.I don't get what's getting wrong, and got a headache after a few hours of attempting to keep track of the correct thread.Anyone an idea what's going wrong, or how I can detect it better? (This is the first time I'm doing real multi threading debugging.
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May 19, 2010
Can someone tell me how to get the selected text in the combo as it encountered cross-thread in the following code:
[Code]...
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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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Oct 27, 2009
This is slightly different to just updating a UI from a worker thread. The object which calls the thread, calls another object, and it is this object which is is trying to update the UI. It doesn't however work.
Imports System.Threading
Public Class Form1
Public Delegate Sub GetText(ByVal sText As String)
Public GetSomeText As GetText
Public Sub New()
' This call is required by the Windows Form Designer.
[Code] .....
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Nov 1, 2011
I've got a List(Of IWorker) which contains a number of concretes. IWorker in turn has a Startup() and Shutdown() method.Inside the Worker class, Startup() creates a new worker thread then returns. Shutdown() presently sets a private ShutDownRequested flag and returns. The flag is checked by the worker thread (at worst every few seconds).This all works fine but at present the parent app has no way to determine if the Worker has finished shutting down.I can see a number of ways around this but am not sure what the best one is.Add a State property to IWorker. Should work but I'm going to be polling states which seems a little nasty.Make the shutdown command blocking - Would probably be my ideal solution but I'm not sure how to implement it - does the worker Sunclock a private object which Shutdown() should also try to Synclock after setting the flag?
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Aug 24, 2009
Here is my setup:
Form1.vb - contains RichTextBox1 and BackgroundWorker1, which calls a the Control module.
Control.vb - calls Display module.
Display.vb - calls Form1.SetTextBoxText("text here").[code]...
My observations: When the Display module calls SetTextBoxText, InvokedRequired's is false. Also, if the BackgroundWorker1 (which is in Form1.vb) calls SetTextBoxText, it works. But if BackgroundWorker1 calls a module that calls SetTextBoxText, it doesn't work.
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Apr 6, 2012
I have a BackgroundWorkerThread which I want to use serially.So some of the code in the UI thread will look like this [code]But of course I can't do the second RunWorkerAsync until the UI thread has seen the RunWorkerCompleted event indicating that the "Sequences" work has been completed (or somehow knows that the "Sequences" work has been completed).So I need some sort of synchronization between the two RunWorkerAsync calls, but whatever I use cannot hang up the UI thread because it has to be able to handle ProgressChanged events.Maybe the RunWorkerCompleted event could make the second call but I really don't like that structure.So how do I delay the second call to RunWorkerAsync (for the "Templates" work) until the background thread has completed the "Sequences" work?
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Oct 20, 2010
I am new to multi-threading in VB.NET and have come across a problem whereby I am wanting to append text to a text box on a form from a service thread running in the background.
The application I am developing is a client/server listener, I have been able to get the client and server PC's to talk with each other (confirmed through MsgBox), however I am now struggling to get the service thread on the server to append the text to the textbox, nothing vissible occurs.
I have a form named testDebug which calls a class (RemoteSupport), this class does all the handshake tasks and updates the textbox with the connection data.[code]...
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Apr 6, 2011
I have searched the forum and found several forums related to the backgroundworker thread but have been unsuccessful in finding my answer.My objective is to display an animated gif or progress bar while the program is executing a particular method which can take upwards of several minutes to complete. I cannot get the second thread to run the progress bar while the main progrem is executing the time consuming method. I have created a demo based on another thread and can't seem to get it to create two threads. I was attempting to get the backgroundworker to execute the progress bar while my main code runs on UI thread.
[Code]...
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Apr 25, 2012
I have a application which processes 1000's datas.. for each processing it needs to update gui and db and many variables in my application. So what i have planned is to use 50~90 background worker with my own algorithm of thread pool, synchronization and thread close.So here is it efficient in terms of memory and performance. just confused what to use.. backgroundworker componenet or standard thread.
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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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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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May 30, 2011
I am testing a background workder. I am running the following code for the test.
Private Sub bgwTest_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles bgwTest.DoWork
Dim a As Integer = 0
Do While a < 10 'Infinite loop
ComboBox1.Items.Add(1)
[Code] .....
But this code generates the following error:
"Cross-thread operation not valid: Control 'ComboBox1' accessed from a thread other than the thread it was created on."
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Nov 3, 2011
I am trying to create a new instance of a form if its not allready been created the only problem is is that the instance creation is inside a worker thread.[code]...
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Aug 6, 2010
I'm working on a web application that uses the web browser control to get and set info from my website. The content on the site is pulled from different pages and the data the application stores becomes really huge so i used a background worker to do the work and keep the form responsive. On each loop i call to get the webbrowser's inner html so i can sort through it and grab what i need and it works; but only the first time!? After i call it the first time and try to call it again to update the variables the function hangs and then the console shows me a Thread Abort Exception, The try statement i used to contain it doesn't fire off an exception. When i debug the program and i get to that function, it hangs and then just stops working.
The function that loops:
vb.net
Dim ids As String = GrabIDs()
Dim IDCount As Long = ids.Split(CChar(",")).Length - 1
Do Until IDCount = 0
[Code]....
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May 27, 2012
I'm getting a Cross-thread operation not valid error when my label text changes - this is very strange because it was working up until yesterday.The only way I can get this to work is by applying the invoke..[code]Is there a more simpler solution or will I have to invoke all my label coding?
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Mar 21, 2011
I use background worker almost daily and works great. Today I came to an instance though where I needed to put my background worker in a separate project then the one I was running because I needed to use this class in two different projects in my solution. When I tested the coding on a winforms form, it works perfectly, handling my coding on the background thread. When I try to reference this class from an external project, all of my coding seems to run just fine, but it does not appear to be doing anything on a background thread as it should be, causing my main window to lockup.
Is there any way around this / what is the best practice for ASYNC calls in an external class.Note I basically created a class that u call start, and an event fires when data is ready, so it's not like my external project is waiting for the method to complete.
Solution ABC has two projects. Project A and Project B. Project A is my WPF application and B is my DLL doing the work. Inside project A I have
Dim SmartCardData as new Solution.B()
SmartCardData.Start()
Project B has a sub
[code]....
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Jan 14, 2009
Is it possible to create a new instance of the webbrowser class inside of a worker thread?
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Sep 4, 2009
I have a standard windows application called winap. I have a com component which acts as an api to the winap. I have a class in winap call classapi which has all the methods that the api calls and all works well. The problem is that one of the methods in my class api needs to get a handle on form elements in the main worker thread. Whenever I try to access an existing form I keep getting null because the for exists in the main worker thread and my api call is in a seperate thread.
[Code]...
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Dec 11, 2011
how to put this on a background worker without getting cross thread errors??? trying to upload a childform object values to an access db.I don't work in IT,Our company's LAN so slow that it takes around 3~5 seconds trying to update/insert values in access using the code below so putting it on a background worker i think makes the app immediately usable once save/upload's called unless otherwise somebody could suggest a faster way to speed things up.[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 23, 2009
I have a windows application that need to process som quite time consuming jobs. In my first try i did all processing under
the form thread. The result was bad response and update of the form due to the heavy jobs.To get around the problem with bad response from the form i created a new class "processing" where i put all the data processing. Then i instanciated a background worker where i in the "doWork" sub created a new instance of "processing".The "processing" class creates a timer from system.timer, and the timer drives the processing.On the Timer event Elapsed the timer starts a new thread from the thread pool.
My problem is now when i want to asynchronously close the background worker (with the corresponding function call what ever it is called ...) there is still a timer thread out there that causes exceptions for me.
1. How can i close my background worker and at the same time have the timer to be stopped?
2. Is there a way to synchronize the timer event so that the timer executes from the background worker thread?
3. Is there a better approach for me to adapt?
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Jun 6, 2011
I am in a trouble with this error:"An attempt has been made to free an RCW that is in use. The RCW is in use on the active thread or another thread. Attempting to free an in-use RCW can cause corruption or data loss." I am not sure if the RCW-error is related to my problem but I was having this error last January 25. It appears when I am ending my application. I ignored it. The next morning when I resumed coding for my application, the changes I am making does not appear at run-time anymore. Whatever GUI changes I make in my application (at design time), it does not make any effect any longer when I am running the application. What is causing this? I am so afraid if I have to restart my application from the scratch. I have gone far.
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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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Nov 25, 2011
I am trying to interface with excel in a vb.net windows app I am writting. Basically it imports csv files to a data table, adds some additional data from with a oledb datasource, creates a view to sort the data before pushing back in to a datatable and spitting it out to a listview. The list view then allows you to further filter and sort the data (or will do shortly but thats not an issue).From the data in the list there are then 2 options, it will either create individual reports for managers in a excel sheet, which it colour bands based on a total field and then emails out to the managers. This works fine.
The other feature is that it produces a summary report that goes to a central email account. Again it creates an excel workbook, adds 4 work sheets, copies all the data to a master sheet (sheet1), it then starts at the bottom of the master worksheet andcopies the total values from the total row for each employee and copies this value in to the next blank column. (This is basically used so I can determine based on the 3 score bandings which sheet each line should go on. The lines for an employee are madeup of individual leave lines and total line that has the summation of the individual lines for them).
Private Sub Button6_Click(sender As System.Object, e As System.EventArgs) Handles Button6.Click
If btState = False Then
[code].....
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Mar 11, 2009
I have the following code that adds a background worker into a VB.net WPF project:
Imports System
Imports System.ComponentModel
Imports System.ComponentModel.BackgroundWorker
[Code].....
And I get the following error for the DoWork worker event:
Handles clause requires a WithEvents variable defined in the containing type or one of its base types.
It seems like it's missing something in the Event declaration, but can't find it.
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May 6, 2009
I'm using a background worker to read a XML file and do stuff in a database i get nothing in debugger but when i run it i get this error... how can i find out where and what is wrong? Exception has been thrown by the target of an invocation.
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May 5, 2012
I am having a problem that I keep getting the following error when I try to run my program.I am trying to make a circle the size of the value of FrameSize.A first chance exception of type 'System.InvalidOperationException' occurred in System.Windows.Forms.dll
This is the details of the error:
System.InvalidOperationException was unhandled
Message=An error occurred creating the form. See Exception.InnerException for details. The error is: Cross-thread operation not valid: Control '' accessed from a thread other than the thread it was created on.
Source=DreamCatcher[code]......
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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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