I'm writing a little online game for sport, but my head's gonna explode as I can't figure out why I can't access my forms controls from my clients DoRead() thread.In this procedure I can still obviously access the controls normally.[code]Tried using delegates and invoking, and setting SearchForIllegalCrossThreads false.
View 7 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.
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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.
I am trying to access a dynamically generated Control from a separate thread. But I am always getting a "Stack Overflow Exception" with my code. I am using following code:
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I have a Windows Forms app that, unfortunately, must make calls to controls from a second thread. I've been using the thread-safe pattern described on the [URL].. Which has worked great in the past.
The specific problem I am having now: I have a WebBrowser control and I'm attempting to invoke the WebBrowser.Navigate() method using this Thread-Safe pattern and as a result I am getting StackOverflow exceptions. Here is the Thread-Safe Navigate method I've written.
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I was a vb6 user, done a few projects only with forums Now i am moving to vb.net(vb2010) and i have some trouble.Lets say we have a form(form1), a module(mod1) and a textbox on the form1.
i want to start a Sub (DoWork) in the module but in a new thread.
Dim Thread1 As System.Threading.Thread
Thread1 = New Threading.Thread(AddressOf mod1.DoWork)
Thread1.Start()
The DoWork sub does some stuff and when it's finished i want to change the text of a textbox1 in the main form and start another sub (DoWork2) on the main form under the main thread not the one DoWork is running under.
Plese do not refer me to another post that mighe give me a part answer, try to explain to me what i have to do and why.
I'm creating a reporting application, and our customers are going to need to generate some pretty big reports which require quite a bit of memory. Ive been in a re-factoring mood lately, so I was wondering what the best way to access the properties of another open form would be(The reporting viewer opens in a new form.) So far I have:
Dim form As MainSelections
form = My.Application.OpenForms(2)
yay or nay.
*Edit - I should probably mention that what I need is a label, two date time pickers, 5 datagridviews and a few datasets. Those cotrols have the info I use for my parameters
I am trying to write general function to set the attributes of the command button and want to access this function from any forms.But I am getting error in this function.[code]
View 1 RepliesMy program crashes with the following error:Controls created on one thread cannot be parented to a control on a different thread.Purpose of the program is to add a control from a thread outside the main thread.Below is the code Private Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
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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 RepliesHow 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 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'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
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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.
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I have a query about dynamically added controls to a form. I have a series of buttons which are created and added at run time. I have a two drop down lists and two buttons which are created at design time. Button 1 creates a series of buttons called "Test 1.x" based upon the selection of the two drop down lists. This works fine and am happy with the logic.However.... Button two should remove all the dynamically created buttons from the form.This does not happen. What does happen is that 50% of the buttons are removed starting with the first one. WHen checking the loop it only enters the loop half the amount of times that there are buttons. Very strange. When the loop is run repeatability it will remove all controls. Why will my logic not remove all the dynamically created controls at once? What is wrong with my logic?
I attach two code snippets and the .net file for your consideration.Button method which creates the dynamically created buttons from the two drop down lists and adds to form
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim Count As Integer
Dim MaxHours As Integer
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I am trying to write an app that in the thread will do some tasks, the form lokks like this:and what it should is something like this:
- retrieve data, populate a row in the listview, increase the first progress bar
- retrieve data, populate a row in the listview, increase the first progress bar
- retrieve data, populate a row in the listview, increase the first progress bar
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I've got a bunch of labels that I update regularly in the program, resulting in lagg, which is bad, so how can I update the labels in a thread?
When I try
Thread = New System.Threading.Thread(AddressOf ShowInfo)
Thread.Start()
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I've been building controls for many years professionally and personally, but even back in VB6 days I just could not work this out. After all this time I remembered about it again.If I create a usercontrol/containercontrol and add one or more controls to the controls surface, I just cannot figure out how to access the controls at design time.
View 4 Replies1) Which one works better? BackgroundWorker or Multithreading?I have to do lots of processing in my application, I'm not too sure how the two of them works.
2) Can I assign controls in a GroupBox to a thread?Let's say I have to login to a certain forum twice with different accounts, so in GroupBox1 (thread1), I'll be logged in with username "asd", in GroupBox2 (thread2), I'll be logged in with username "zxc", and I have to do lots of processing (mostly html parsing) from there. Is this possible without stressing on memory usage? I'd like to keep my program memory usage under 10k.
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I'm trying to dynamically add a control to a form from an event that is raised from an asynchronious socket's thread.
In other words, when I get an OnDataArrival event is raised from the socket thread, I raise DataArrival event in my form. The form's DataArrival sub then tries to create and parent a control.
Whenever I try this, I get the following error: Controls created in one thread cannot be parented to a control in a different thread.I know a bit about delegates and invoking, and I think that's how to solve this problem, but I don't know where to declare the delegates and how to use them.
Ideally, I want a delegate/invoker to handle the DataArrival sub in the socket class so that everything that happens after that will be thread safe. Can this be done?
In main thread I create panel(s) (based on some configuration), and then in the next step based on the file type (like video, ppt, image...) I create appropriate controls (dynamically) to show on the forms.
The creation of the control will be done in separate threads (for each file). After creating the control, it throws an error when I try to add that control to the panel (which was created in the main thread), something like cross thread violation, control was accessed from one thread other that it was created.
Can some one please help me in this regard? In this scenario, everything - creating the panels and controls - will be dynamic. Nothing will be static.I tried some of the articles found here on StackOverflow (like, control.BeginInvoke() .. etc), but wasn't able to solve my problem.
how to access the main ui's labels from a delegate method?
View 7 Replies[URL]
In my program, I created a list of a class that contains 5 picture boxes, a button, a label, an identifier, and some other stuff. I've got roughly 65 of these in this list. I'd be stupid to hard code all that in. The identifier is a 2nd way of identifying which specific location I'm working on.
Anways, all this is created at compile time. Works perfectly fine.
I then manually start a background worker that pings a collection of components. Based off the success of those pings, the picture boxes are enabled or disabled. Basically a proactive way to see if a collection of devices over multiple locations are actually working.
It's the background worker that fails because of thread-safe calls.
Private Sub bgwStatus_DoWork(ByVal sender As Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles bgwStatus.DoWork
Dim status As Integer
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I would like to know how do .net developers manage a large window application with a large number of controls, such as textbox , button, groupbox? I have seen a number of people do it this way : declare the controls as an array and initialize them one by one at run time . In this way it is easy to manage those controls because they can be accessed by array index; but this solution seems to require very good understanding of control's attribute such as its location, font etc. This could be a difficult task if the project is passed on to a less experienced developer and add changes to it.How do you deal with it?
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()
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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).