Is it possible to edit/get data from a DataTable from another thread? On one form, I'm declaring a DataTable and loading it with some data. On the same form, I have a sub wich does some updates to the DataTable.
Now, I want to call that sub from another thread, but it seems like an impossible task... When I for example do a 'for each' in the sub wich updates the DataTable, it doesn't actually refer to the DataTable. All the rows and columns are not there.
I've been reading about some cross-threading and found some example where the objects invoke-property is used. But the DataTable does not have a invoke-property. So, how is it possible to do what I'm trying to do? I've been searching the forum/web for a while now, but maybe someone here can point me in the right direction?
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.
I have a small problem that I am sure is due mostly to my inexperience with threading. I have used simple entirely self-contained threads before, but not to a great extent. I understand the basic laws that surround them, such as how a thread cannot access another thread's member directly, and must use delegates.
I'm working with BackgroundWorker, I want the BackgroundWorker do the retrieval process of data from database while the user can still do another task on the form. The problem is, after retrieving the data, I can't seem to access the ListView in my Form from the DoWork event of BackgroundWorker, I will populate that ListView using the data I've retrieved.
Consider this example, this is how I'm doing it:
Public Class Test Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
im trying to terminate a threading.thread using thread.abort the thread runs a download connection so is usually in the middle of socket.recieve or socket.send or socket.connect when aborting i just want to terminate the thread no matter what thread.abort raises an MDA excpetion. so i ticked it off in the debug exceptions menu. now it doesnt raise an exception, but the thread simply wont terminate. my program wont close unless i press top in the debugger.i cant pause downloads because i cant terminate the thread this code wasn't working?
Dim vT As Threading.Thread For Each vT In clsDownloader.DownloadThreads If Not vT Is Nothing Then vT.Abort()
[code].....
as for the exception concerning threads being aborted from other threads being dangerous, how is it possible to send a message from a main thread to another thread to abort itself? as far as i know the only way to a abort one thread from another is to just kill it (because i dont know of ways for a thread to communicate with another).
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?
I'm firing a thread to unzip a file. I need some way of indicating to the parent that the unzip thread has ended. I've tried raise event in the unzip thread to a sub in the parent but this runs the sub from the unzip thread. With ApartmentState set to STA, so that I could use a save dialog, this was OK until I displayed a messagebox which was hidden behind the main UI(and whatever I did I could not get it to the front).
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".
"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.
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
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).
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.
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
I have an application that I need to load data in a background thread and make available to a combobox or list box on my main form or UI Thread. I am really new to threading in VB and how to best accomplish this. Here is some code from a test project:
I have troubles with processing callback method invoked from a C++ DLL. Imagine: there is a ListBox on a Form; I wish to fill it with Items from callback. In Debug mode, I got a System.InvalidOperationException, because I access ListBox methods from different thread
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.
I've got a problem. I'm running a different thread. The thread's sub is looping, doing various things during the program, and eventually tries to close the form. I get an error, because the other thread can't access the "Me" object, I guess. It won't close the form. I don't want to use Application.Exit. Is there another way?
I cannot access datagridview from another thread...it says that cross thread operation is Invalid... if I use: Form1.Label1.Text = "From another thread" No errors but no update on Label1.Text as well....
I can't seem to find a good tutorial on how to access uithread components from the background thread.. It seems like there is different means of accomplishing this. I'm not picky about which one I use.
