Multithreading - Thread Of Execution In .net/COM Dll?
Jun 23, 2012
According to the answers to another question, the VB user interface cannot be updated if the thread that created it is busy: hence why big computational jobs usually have to go in a background task.Here's what's mystifying then. I have the following code. It's called over in-process COM, like this
client calls showform()
client does loads of work, freezing up its own UI in the process
client finishes work, returns to updating its own UI
At step 2, the VB form is there but frozen - you can't interact with it. At step 3, the VB form becomes usable. But why is this? Surely the thread of execution has returned to the client? If the client is somehow handling events for the form, by what magic did it know what events to handle and where to send them?
[Code]...
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Aug 19, 2009
I have a vb.net application that uses threads to asynchronously process some tasks in a "Scheduled Task" (console application).We are limiting this app to run 10 threads at once, like so:
(pseudo-code)
- create a generic list of 10 threads
- spawn off the threadproc for each one
- do a thread.join statement for each thread to wait for the longest running one to complete.
What i am finding is that if the code called by the threadproc contains any "Debug.Writeline" or "Trace.Traceinformation" statements, the thread hangs. I can see the thread in the Debug - Windows - Threads window, and switch to it, but it highlights the debug.writeline statement and never gets past it. is there something special about the Debug or Trace statements that make them non-thread-safe? Any idea why this would hang things up? If I leave the debug statement in, the thread never completes. If I take the debug statement out, the thread completes in less than 5 seconds.
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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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Mar 13, 2012
I am running code in a thread upon opening an Excel workbook that takes some time to execute. If I attempt to close the workbook while the thread is still executing, giving me the standard prompt to Save or cancel, my thread is interrupted (not sure if "interrupted" is technically the right term) when I click Cancel. More generally, it seems that UI interactions/updates cause the thread to be interrupted.
Is there a way to either 1) prevent the thread from being halted by a UI update/user interaction, or 2) allow the thread to resume after being interrupted?Nothing fancy about the code:
Private Shared Sub Test()
Dim t As New Thread(AddressOf DoSomethingThatTakesAWhile)
t.Start()
End Sub
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Feb 10, 2011
I'm trying to safely kill a thread. In my button click I have:
try
dim bar as new foo()
dim mythread as New System.Threading.Thread(AddressOf bar.Start)
mythread.Start()
[code]....
When it goes to abort the thread I still get a thread abort error.
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Apr 29, 2011
I have this code:
Public Sub Submit(
ByVal reasonId As Integer,
ByVal email As String,
ByVal message As String
)
'[Argument validation code here]
EmailController.sendMail(reasonId, email, message)
End Sub
I want to spin this off in a new thread so Submit() returns right after creating and start the thread.In C#, I could do something like this:new Thread(() => { EmailController.sendMail(reasonId, email, message)}).Start();
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Oct 17, 2010
I have a webservice with a webmethod that accepts an XML from a client via POST (don't know if this really matters), validates XML and the data inside, and then processes the XML and returns an answer to the client.At moment, I have a problem with large XMLs; it takes too long for the XML preprocessing to finish, and the clients timeout expires.
Instead of increasing the timeout of the client I thought I could maybe separate the XML validation from the XML processing by starting a new thread after the validation which processes the XML and at the same time return the validation answer to the client. (the processing won't start if the XML is not valid.
Now my question is: Will opening the new thread increase memory usage? normally I would guess it will (for normal applications) but here I am returning an answer to the client and essentially ending the process of the main thread.
Imports System.Web.Services
Imports System.Web.Services.Protocols
Imports System.ComponentModel
[code]....
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Jun 11, 2009
I have an application which has a thread running which makes constant calls to a server. Occasionally, the calls become unresponsive, and I would like to stop and then restart the thread.How do I do this? I can't use mythread.Abort() because then it doesn't allow me to start the thread again.
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Nov 18, 2011
I'm in the Progress of changing a big Application from Singlethread logic to Multithread logic. I'm currently move Dataloading Logic into a sperate thread, and work with callbacks after they are finished. I have Synclocks in place in order to ensure threadsafty. But sonetimes the Synclocks wait even if there is no other thread with the same synclock active. Is there any way to find out what witch thread they are waiting for, and why? BTW, I have FW45 installed, may that be the reason, since it'S a inplace upgrade for FW40?
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Jan 24, 2012
I am making use of a serial port in a class. I am raising an event from that class to my form calling the class. Event contains data received... I wish to simply populate a textbox from the raised event.Now I am not specifically creating a seperate thread, but I get the normal crossthreading error when trying to update my textbox on the UI, so my assumption is that the serial port and its internal methods probably creates its own threads...Regardless, I am a bit confused as to how to properly implement an invoke, from my main form, pointing to the thread in the instantiated class...
Dim WithEvents tmpRS232 As New clsRS232
Private Sub but_txt_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles but_txt.Click
tmpRS232.Set_com_port("COM8", 38400)
[code]....
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Apr 20, 2011
How do I ensure that a process has a thread on each processor?
What I am asking is how do I address processors to ensure a thread is running on it?
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Apr 27, 2011
I feel like the answers I seek are rather obvious so I feel silly for having to ask, but I just can't seem to figure this out (I'm new to threads, and am really only comfortable using them in Java at the moment). I have an Excel Addin application created with VB.NET, and I've noticed that occasionally while it's running some code (it's no one specific block of code) the program execution will just stop. This is especially problematic when I've set ScreenUpdating to False for Excel because the users then have to completely close out of Excel to get ScreenUpdating to true.
[Code]...
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Mar 23, 2012
I created a background thread that get's data and returns it to the main thread; this works. Now I want to be able to stop the SQL request from the main thread (probably on a button click). This is my test code for creating the thread (working):
[Code]....
How can I access the background thread to stop the query on demand? Do I need to set a flag on the main thread telling the background thread to stop running then have the background thread poll the main thread at intervals? I was trying to look for an example but I wasn't able to find a good one.
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Jan 21, 2012
It's easy to do so in objective c but I do not know how to do so in vb.net update:I know about control.invoke. But control.invoke requires a control that may change from program to program. What would be the easier way?So yes program is winform. However I need a solution that does not depend on any specific control. If that's the case actually I do not need things to be run on main thread do I?
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Dec 1, 2011
I am building a code library to be used by a 3rd party developer. Neither my code or the 3rd party have any UI controls involved. It's purpose is a combination of providing the ability to look up information from a database while at the same time polling it and throwing events when a set of conditions are met. Naturally the only way it's going to be responsive to the 3rd party library's commands is via multithreading since everything in a single thread stops once you start polling the database.
The sub I am using is part of an object that I create in the main thread and attempt to have it run via a thread, when a condition is met I have it update a property in that object, throw the event (or execute a callback in my latest attempt) and then attempt to have a simulator for the 3rd party control read the property.It's easy to setup the multithreading part, the hard part appears to be throwing the event so it is seen in the original thread and the data is available there. Any attempt to do this generates a cross thread error when the data is read.
I attempted to use delegates and calling methods asynchronously and using the callback function but still get cross threading errors.Is my only possiblity to use a background worker, using either the progress changed or runworker completed events? Even then am I going to be able to set the property in the function from one thread and read it in another?
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Aug 13, 2011
I'm having difficulty in working with MultiThreading.I want to add to my project a ProgressBar to show the working flow.I'm getting combinations from many Strings, the number of combination can be really big, so it takes few seconds or minutes.
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Oct 30, 2011
The error occurs at: For i As Integer = 0 To txt_load.Lines.Count - 1..The project exists of 2 rtb's. One with a list of lines. The other will be filled with the converted lines. The main reason that I use it is that I want to use the app during the conversion. The second is that I want to learn how this works.[code]
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Jun 4, 2011
Right now I have a Email class that has all the properties of an email to send it, and then a SendEmail function which takes those properties and uses them in the following
Public Function SendEmail()
'Exception handling
Try
[Code]....
The loop goes through each email in the array to process its email, however with the multithreaded function I cannot call
"EmailArray(i).ThreadSendBatchEmail()"
So how do I call an objects method when its on a different thread?
And I'm making it multithreaded so I can easily pause the process, and because the program freezes when the send() function is working, this would resolve that.
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Nov 14, 2011
I have a per-call WCF service that serves a number of clients. I'm looking to speed up the services by running some background processes so they don't block or slow down the main function of the services.
One example is that the main function needs to return a set of data, while the background thread needs to record some statistics based on the parameter(s).
Code:
Public Function GetAccountDetails(id As Integer) As AccountDetails
Dim retVal As New AccountDetails
Dim a As New Accounts
[Code]....
If I use this background thread to record the statistic it doesn't block the main thread from returning the data to the client.
It's been working well in test scenarios, but my question is, are there any dangers with leaving this thread to execute without Joining it before returning the data to the client? Could there potentially be any loss of statistic data? Could there be potential memory problems on the server side?
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Jan 13, 2011
I am trying to implement a solution for updating form controls without using a delegate.
Imports System.ComponentModel
Imports System.Runtime.CompilerServices
Public Module MyInvoke
[code]....
I get a cross threading error as though i didnt even use this method:Cross-thread operation not valid: Control 'ComboBox1' accessed from a thread other than the thread it was created on.
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Feb 2, 2011
There is a problem with standard System.Timers.Timer behaviour. The timer raise Elapsed event with some interval. But when time of execution inside Elapsed event handler exceed timer interval then thread pool begin queuing event handling. This is a problem in my case. This is because with my Elapsed event handler I fetch some data from database and doing something with it and finally save results back to database. But data handling should be provided only once. So, is there a way to prevent from queuing elapse events for System.Timers.Timer.
As illustration for this issue you can consider next test program:
[code]...
2) Second way is about SynchronizingObject, but it is a valuable only for Windows form application or required additional development of code for implementing object that would be implements ISynchronizeInvoke interface. More about this way you can find here
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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 13, 2009
I have a dictionary object (let's call it _do) I am using to cache some values for use in a multi-threaded program. I have a single controlling parent thread, with a timer function _doTimer() which can kick off child threads with a new instance of class MyThreadObject in each. My parent thread has _do as a property and with each time _doTimer() gets called, it may or may not repopulate _do depending on cacheflag settings. I pass a reference to _do to each instance of MyThreadObject and those threads at some point read the values of _do but DO NOT write to it.
What I want is to ensure that the child threads do not try and read _do whilst the parent thread is writing to it. Same thing but very slightly different -> I also don't want the parent thread to write to _do whilst the child threads are reading from it. However there is no problem with 1 child thread reading the values of _do at the same time as another child thread is reading the values - so ideally I do not want each child thread to completely lock out read access, only locking out Write access.. The code is roughly like this:
[Code]....
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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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