I cannot grasp this issue. In the below code. I am trying to start a separate thread to display a progress bar while a function is executed in the main thread. The function can take a while, and during that time the program appears to just lock up. So, the progress bar does not really need to show the progress it just needs to cycle till the main thread function is done executing so that people know that the program is still running.
[Code]...
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).
View 1 RepliesMy 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 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))
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.
View 4 RepliesI 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.
[Code]...
How do run processes synchronously from a thread or backgroundworker thread? Is it even possible?We have program that allows the user to download several files from a remote server, compress them, and then email the files.It has several long running processes that must run in order. We want these to run on a separate thread so as not to make the form unresponsive. Does a way exist to do this? We attempted a rather clumsy way of approaching this problem by using background worker threads. When each thread is completed and returned back to RunWorkerCompleted, we start another background worker thread and repeat the the next process. It works somewhat but seems to take a lot of resources to run.
View 1 RepliesI have a couple of threads running. One is a trigger which picks up a system event, the other processes stuff. When the trigger picks up the event I want it to notify the processor thread to do stuff. The threads are both started within the same class and can access the thread-object of the other thread. How do I set up the function call though?
View 10 RepliesSo from the comments section where this persons code was translated to VB.NET on [URL]it shows a little code to aid in calling cross thread UI stuff.
<System.Runtime.CompilerServices.Extension()> _
Public Function SafeInvoke(Of T As ISynchronizeInvoke, TResult)(ByRef isi As T, ByRef [call] As Func(Of T, TResult)) As TResult
[Code]....
Error 1 Data type(s) of the type parameter(s) in extension method 'Public Function SafeInvoke(Of TResult)(ByRef call As System.Func(Of frmLogin, TResult)) As TResult' defined in 'GvE.Globals' cannot be inferred from these arguments. Specifying the data type(s) explicitly might correct this error. C:GvEGvEfrmLogin.vb 37 9 GvE
I'm calling that code from inside a method defined in a form but that method is being called from another thread.
Just trying to avoid delegates and this is what the code above is supposed to do, but just can't get it to work.
A thread listens for incoming information from a server will add the received string to a custom control (containing a textbox and a listbox, I've called it console). This requires an invoke so I used the following
Dim InvWriteCons As Console = Gary.ChatCons
Dim INvWriteText As String = "DEFAULT"
Public Sub InvWrite(ByVal cons As Console, ByVal message As String)
[code].....
when I try to perform a cross thread call to fill a text box with messages with the following code I have no problems:
Delegate Sub SetTextCallback(ByVal [text] As String)
Public Sub SetStatusBox(ByVal [text] As String)
If Me.statusBox.InvokeRequired Then
[code]....
However, I am having problems when I use the following code to do a cross thread call to close a form. The form just hangs there.
Public Delegate Sub setFormClosing(ByVal ctrl As Control)
Private Sub closeForm(ByVal ctrl As Control)
If Me.InvokeRequired Then
[code]....
I created a STRING SEARCH function in C/C++ - and I'm trying to use it in a multi-threaded situation in VB. I started this problem in a thread in the C/C++ section of the forum - here [URL] my last post shows me getting this error trying to call the function. Ran the code - got to that point - and in the immediate window I did
[Code]...
I'm working on a website where we'll be getting a lot of videos to be uploaded. To keep things simple and secure, I'm just writing VB.net windows app to suck all the files in a directory in, allow you to set some options, and start the encode by spawning a new FFMpeg process.
[Code]...
I have 5 projects within the same solution file, Im trying to access a form that is part of one of the projects from my startup project.I have looked through the earlier threads and most of them deal with calling forms from within a project.To my understanding ive correctly added the projects to the solution file from File --> Add --> Existing Projects.I have also referenced my Project2 from Project1 but still the intellisense does not let me access form1 of project2 from project1.
View 3 RepliesIm loading a form to retrieve customer information from one form, then, when I collect the data, im trying to pass an ID back to the form that originally made the call. So, what I did is I made it so that the second form calls a sub on the first form, but for some reason it wont work. I put breakpoints in to check the variables, and they are getting data, but I can set the textbox on the first form with the data that is in the sub. Heres the code that loads the second form
Private Sub btnCustSearch_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCustSearch.Click
Dim strLastName As String
[Code]....
I have defined a function on one form. I have to call that function again on another form. Is there any way I can do it without redefining the function again and again?
View 2 Repliesi am trying to use a login form that is used to login after you select one of 7 forms. this login form calls a function that validates then it calls another function, if it's true, that will load the appropriate form.
here's what i have.
vb.net
'Here are the appropriate variables
Public FormName As Form
[Code].....
how should I go about starting to create a Win32 application interface to help user register an account from a website.The website have a form with a lot of controls which is not mandatory field, so my task is to create a form with a few controls and submit to the web server.What is the method that I should read about, is it HTTP Post/Get related thingy or is there any sample on how can I communicate the form action?
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()
[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".
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()
[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.)
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
[Code]...
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.
[Code]...
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]....
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
The project requires a form that has textboxes for a students name and the amount of books they have read, and a label where the points they have earned for their reading is displayed. Also a seperate form with About information and yet another seperate form for summary information.
View 1 RepliesI have a question regarding VB.Net and Object-oriented programming.
I have a solution consisting of two projects.
One project is dedicated to the logic of the application, and one is only to show the Winforms form, and to reflect changes made in the logics project. In other words, when an array filled with various attributes residing in the logics project gets changed, then these changes should be reflected on the form (not that strange in theory).
Here comes the - for me - really tricky part:
I have created user controls, and these are residing in the forms project and placed on the aplication's form. When I click on any one of them, their respective onclick sub gets called okey, but how can I send a message to the logics project from their onclick subs? Basically, I'm not sure on what should be private or not, or possibly how to call the other project correctly. In any case, I can't get it to work.
To sum up: What I need is a line of code calling a class in another project, and someone telling me what should be private, static etc.
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]....