I have a multi-threaded application with several datasets that are read/written to from a couple threads. I have read that datasets can handle multiple readers and one writer. I have synclocks around all dataset writes and no synchronization around reads. I am experiencing random "Index was outside the bounds of the array." exceptions where a dataset item is in a conditional statement, for example:
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I have application in .net 2.0 in which I have a DataTable object globally in my application and have different dataviews in whole application.
When an action performed i have create many threads lets say 5 in which data is read from different dataview, meanwhile while 2/3 threads are reading data(not all 2 more left to read data) a thread write data in datatable. So we get exceptions like "Enumeration update" or "parameter not null" type.
I have use ReadWriteLock for this but do not find any luck it gets stop on ReaderWriterLock.AcquireWriterLock().
Lets say we have this code that runs in the constructor:
Dim initVectorBytes As Byte() = System.Text.Encoding.ASCII.GetBytes(initVector)
Dim saltValueBytes As Byte() = System.Text.Encoding.ASCII.GetBytes(saltValue)
Dim passPharse As String = GenerateKeyString(EncryptionKey)
Dim password As Rfc2898DeriveBytes = New Rfc2898DeriveBytes(passPharse, saltValueBytes, passwordIterations)
Dim keyBytes As Byte() = password.GetBytes(CInt(keySize / 8))
mSymmetricKey = New RijndaelManaged()
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is it ever possible to write locking-features(for threading) with the language itself (this question is purely academic, I know no one will ever do it even if its possible (not me))?
A) In Java, is it possible to write thread safety functions with java alone, but without using any of the provided classes/language elements/syntax which offer this feature?
B) In C#, is it possible to write thread safety functions with C# alone, but without using any of the provided classes/language elements/syntax which offer this feature?
C) In Vb, is it possible to write thread safety functions with Vb alone, but without using any of the provided classes/language elements/syntax which offer this feature?
I have a Console app that loops through a queue and processes each record in a datatable. Each process is long and time-consuming (connecting to a remote website, downloading files, reading them and adding them to the database). I'm trying to implement threading for speed's sake but am having cross-threading issues. (The job takes 8 hours or so to run and the cross-threading doesn't start happening until a couple hours into the run.)I'm trying to figure out how to make my code thread safe. I don't update or rely on any non-local variables, and I don't need to return anything. I've tried locking which works but defeats the purpose of the multiple threads. What other things should I be looking for?
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I sometimes come across patterns or common practices that I do not agree with. I have a clear opinon of what is considered "good design", which is mainly based on my understanding of abstraction and creating layers.IMO, the core of an application is it's object model. It's a hierarchic model where one object references other objects or lists of them. That's a memory-internal model. For example, a house object references a list of rooms referencing lists of furniture.An object is identified by it's reference. There are no IDs or PKs in that layer.Saving/Loading data is an additional feature. Sure, no application will do without, but it's based on top of the core of the application. I could write an application that works very well without loading/saving, and for version 2 I will think about whether to save data to a database or an XML file. Merely this fact proves that a database layer is not the lowest. I've never agreed with that three-tier model - even if you call me unteachable.
In addition to all application objects, there are Datasets - and that's my problem now. They can be considered as a copy of what is already present in the application's object model. Its from a different, table-oriented view. As both structures exist in parallel, there's the need to synchronize the DataSet with the (rest of the) application's objects.That's the task that I am always struggling with, and I ask how you handle it. I know this is a major design question but, fortunatelly, I could quite get around this problem so far.The only solution I can imagine is maintaining additional relation lists. For example, whenever the property of a room object changes, that change must be reflected in the associated DataRow in the DataSet. For this purpose, I need a look-up table that tells me the PK of the given room in the database. It requires a lot of additional efforst to do all the synchronization.Again, the house or room object itself does not have a PK and it won't get one because on that layer, it doesn't even know that a database exists.
I have an application in which I am running a separate thread.
Dim thread As New System.Threading.Thread(AddressOf Main)
thread.Start()
However, the thread makes reference to an textbox named Output, and it generates this error upon execution:
System.InvalidOperationException was unhandled
Message="Cross-thread operation not valid: Control 'Output' accessed from a thread other than the thread it was created on."
Source="System.Windows.Forms"
(message shortened for space)
How can I make the operations run on another thread, but still use the Output object? I cannot call a subroutine to do that for me, as it generates the exact same error.
The method called is AppendText, by the way.
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?
I am currently working on an application which requires reading, writing and modifying data from a TEXT file. I have searched a lot but was not able to find a simple way to achieve this. I have to use a standard VB form with textboxes for ths text file opearations. s
View 1 RepliesI am currently working on an application which requires reading, writing and modifying data from a TEXT file. I have searched a lot but was not able to find a simple way to achieve this. I have to use a standard VB form with textboxes for this text file operations.
View 2 RepliesMy application works with the sql database. It always connect to the databse using the same login and password written earlier in the application code.I just have a conncetion string with all that data inside.
I know that it is not the safiest way to do that. How to safely hold this thata inside of an application?
I am using the Interop User Control Toolkit to create a user control for use in a VBA Forms "like" environment. I created a user control and it worked just fine in the environment. The problem that I have is that I get an activex warning upon form load. I need to get rid of this message. I have tried this link with no luck... Although everything compiled file, it crashed my VBAClnt.
View 1 RepliesI am instantiating a form object in my code behind the dataset just to access some form level variables and to occasionally set a label in the navigator bar. Recently in the b2 Team version of VS2010 there are some strange errors thrown in the immediate window and then I'm tossed out of debug mode and back into the IDE. This code has been operating for some time in this project without this behavior. A team member has just reproduced the behavior in his development machine also.The error that starts the shutdown of the debug instance is this: Control accessed from a thread other than the thread it was created on.
View 4 RepliesI am going to implements a thread pool to run my application. All of my content is saved under a folder on my desktop.
Each of the files are in .txt format. How can I read each .txt from a given folder and then put the .txt file into the thread pool / thread queue?
Basically it's this question but then for VB.net. I need to check the CheckBox state from another thread than the main thread. Solutions for the linked question contain C# code. On-line translators do not yield understandable results.[code]...
View 1 RepliesI am going to implements a thread pool to run my application. All of my content is saved under a folder on my desktop.Each of the files are in .txt format. How can I read each .txt from a given folder and then put the .txt file into the thread pool / thread queue?
View 2 RepliesIn 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()
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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".
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.
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()
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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.)
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
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
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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)
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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).
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.
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.
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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
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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:
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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
On a given application form, I have around 20 controls that I need to set in the main form. I have a separate thread that only needs to ready some properties from the controls on the application form It will never try to write to the form's controls.
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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
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I have added a DataSet to connect with my SQLDatabase. Test Query displays correct values but when I programmatically try to display the value of a certain field using following code
dim vrName= dsTest.Tables(tblTest).rows(0).items(0)
I get Tables is not a member of dsTest.
how can I use dataset to read, write, edit and delete data as we use in WinForms?
Here is my code. clsRules is a class with Get set properties. I have to read data into list and then add to dropdown. There is a reason I am not directly adding dataset into dropdown. That may be part II of the problem.[code]
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