I'm using Visual Basic 2010I've created a ListBox and a BackgroundWorker using designerI want to change the location of listbox using backgroundworker but I get the error as follows:"InvalidOperationException was Handled by user code:"Cross-thread operation not valid: Control 'ListBox1' accessed from a thread other than the thread it was created on
View 10 RepliesI recently read about using SynchronizationContext objects to control the execution thread for some code. I have been using a generic subroutine to handle (possibly) cross-thread calls for things like updating UI controls that utilize Invoke. I'm an amateur and have a hard time understanding the pros and cons of any particular approach. I am looking for some insight on which approach might be preferable and why.Update: This question is motivated, in part, by statements such as the following from the MSDN page on Control.InvokeRequired
View 1 RepliesI want to execute a few external apps, where in between a RichTextBox gets updated.. Say when program1 has been startet the RichTextBox is updated.. And when program2 has been startet the RichTextBox is beeing updated again.So what i've done so far is this:
Public Class Form1
Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
[code]....
But when doing the above i get the following error:
Quote:
Cross-thread operation not valid: Control 'RichTextBox1' accessed from a thread other than the thread it was created on.
I'm adding multi-threading facilities for the first time. I have a function that is wrapped to be run in a separated thread. This function retrieves data (text) from a combobox and it works for sure without multi-threading.
When I call it as multi-threaded, I get the following error when I try to retrieve the data from the cmobobox: Cross-thread operation not valid: Control 'cmb1stBL' accessed from a thread other than the thread it was created on.
It looks like a restriction of thread-safety... I assume that the child thread cannot read from his parent, to make sure that he doesn't change his parent data. So how can I read the data from the combobox? Should I read the comoboxbox data before calling the child thread?
What do I want to achieve: I want to perform some time consuming operations from my MDI winforms application (C# - .NET). An MDI child form may create the thread with the operation, which may take long time (from 0.1 seconds, to even half hour) to complete. In the meantime I want the UI to respond to user actions, including manipulation of data in some other MDI child form. When the operation completes, the thread should notify the MDI child that the calculations are done,so that the MDI child can perform the post-processing.Should I use explicit threading (i.e., create explicit threads), thread pools? Or simply just propose your solution. Should I create foreground or background threads?And how does the thread communicates with the GUI, according the solution you propose?
View 7 RepliesI have this situation where I want to set the visibility property on the form but I have a cross threading issue. I have coded it like the following but is it possible to achieve it on the property on itself.
[Code]...
I've problem with my application. I have one class frmMain, where I have one Listbox. I'm developing a separate class that lunches a couple of threads. They do some work, and in the end I want to show the data in the frmMain listbox. I'm using the following code:
One sub that handles the requests to the Listbox. I declare it in Module
Module Functions
Public Sub ChangeText(ByVal ctrl As ListBox, ByVal str As String)
Try
If ctrl.InvokeRequired Then
[Code]...
I have an application with two forms - a splash form and the main form. The main form reads an XML file and displays data from the file in a rich text box. While that is happening the splash form is displayed. When the main form is ready to be displayed the splash form closes and the main form is displayed. I have a progress bar on the splash form to inform the user of the progress of the load. I want to set the maximum value for the progress bar to the number of elements in the XML file. In the main form I am using a reader to count the number of elements. After I get that number I wan to update the maximum on the progress bar control so it displays correctly. That is where I am getting the cross threading error. Now I could do that in the splash form. But where the real issue lies is I want to update the progress bar value every time I read an element in the main form process to read the XML file. That I don't think I can do in the splash form as it would duplicate the process of the main form and defeat the purpose of the splash form.
I have researched this issue but can't find an answer. I have tried the delegate route but I still get a cross-threading error. I assume that is because I am cross threading across forms.
I'm attempting to communicate via USB to a hardware device. So far I can use CreateFile, ReadFile and WriteFile to communicate with the device efficiently, but occasionally the WriteFile call will hang because there is no device located at the port where it was installed. I have the WriteFile and ReadFile calls in a managed thread that I use the Join() method on to return control to the parent thread.
View 17 RepliesI am a student attempting to learn VB.NET on my own. Today I wanted to tackle the BackgroundWorker component. I found an excellent article online: How To Use a Background Worker. I successfully completed the walkthrough and even performed the "adventorous" part that dealt with working with controls updating across threads using delegates.Now I came to a part that I didn't understand how it was working. To summarize the following code, I have a delegate that has a Label and a String in its signature. I then have a subroutine that is called on the worker thread. Inside this subroutine the delegate is created and (I guess) ran again so that it is on the same (Main) thread. Please correct me if I'm wrong here.
Here is the method is performed on the worker thread:
Private Sub My_BgWorker_DoWork(ByVal sender As Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles My_BGWorker.DoWork
[code].....
I've been reading around trying to find out why I'd be getting this exception to no avail.
I'm using Visual Basic 2010.
Briefly, I have a "Settings Panel" form which takes a while to create (it contains a lot of labels and textboxes), so I create it in another thread.
After it's loaded, it can be viewed by clicking a button which changes the form's visibility to True. I use the following subroutine to handle invokes for my controls:
Public Sub InvokeControl(Of T As Control)(ByVal Control As T, ByVal Action As Action(Of T))
If Control.InvokeRequired Then
[Code]....
The SettingsTable.Create() method generates a bunch of Labels and TextBoxes based on the contents of the application settings and adds them to the SettingsTable.
When I click on the ViewSettingsPanel checkbox, I get a cross-thread violation error.
I have a relatively simple question regarding the best way to call the DataGridView.Rows.Add function when it is inherited into the current control. Which is the best way to make the call to the inherited control? Call it directly in the invoke or call it using recursive-like function? They both seem to produce the same result, a row gets added and the quantity is returned, but which is the most efficient?The delegate: Private Delegate Function ReturnDelegate() As Object
The two ways are:
A)
Private Overloads Function AddRow() As Integer
If InvokeRequired Then
Return CInt(Invoke(New ReturnDelegate(AddressOf AddRow)))
[code]....
I looked around the site and the questions I found relating to this subject were for C# (the application that I am maintaining is written in VB.NET), so I apologize if I overlooked one. Here is where I am calling my thread:
[Code]...
I've not got any issues with Cross threading but I hate the amount of work involved in sorting cross threading issues out.I thought today that my inherited Listview Control could have built in cross threading capabilities; it would decrease the amount of work on the form, and tidy things up.I've got this to work (EnsureVisible method), BUT I'm a little stuck when it comes to the Items.add below is my example control.
[Code]...
i m working on an application where i m using multi threading.suppose i ve below threads
Thread1
Thread2
Thread3
so i want to call a method from some specific place where every thread running concurrently
[code]...
so i m not able to identify a thread in the case "ABC"
In my API class I encountered a lot of times I had to Get/Set low/high order <something> of <something>. For example, get the low order integer from a long. I made a few functions for this: [code] Before I start using these functions permanently, I come to ask if it contains any bugs, especially because of the Unsigned/Signed issue.
View 15 RepliesI am looking for an advice how to do a drag and drop copying an object anywhere on the form and also move an object around and place it where the user wants. Is that possible? Kind of something what we have in the designer of Visual Studio, we can drag and drop a label or a textbox down on the form.
View 7 RepliesI was wondering if you could offer a hand on something I'm finding a bit tricky.I am looking at basic shell integration. That is, when a user right clicks a file they can select an option that I have specified. Clicking this will allow them to do various functionality. The way the shell is working for me is that I have a registry entry which runs a specific file. That's all well and good but I need to communicate with a process that is already running on the local machine. (To prevent the users from having to enter login details multiple times).
So I need a way to launch an application, which can call a function in a process that is already running, and pass through the file path. The other application takes the filepath and does whatever it needs with it.
I have both separate sides of the application working (it can get the file path fine, and the other application knows what to do with a file path). The problem I am having is actually linking the two together.
This code is from [URL], so I assumed it would have worked, but I am probably missing something simple.
[Code]....
When I run this code, I get an InvalidOperationException (cross thread operation). How can I get my progress bar on the second thread, or does it have to be created at runtime on that thread?
Frankly, NONE of this makes sense to me..[URL]..They just jump right into code without baby steps that explain the situation.Every other aspect of VBnet has been well spelled out to me and I get it -- but this business of using the serial port and going nowhere because of a cross thread error has me 100% baffled.
If anyone can point me to a tutorial that really explains it simply and well (without jumping into friggin' code).Even in the above link, they show 3 different techniques of addressing the same problem ! (Like I CARE
I'm trying to set the text of a ToolStripStatusLabel in a form, wich contains some ToolStripStatusLabels, a ListBox and a button. I'm setting the text from a BackgroundWorker wich is started from a timer. I thought this would be okay. Well, the problem is that sometimes it works, and suddenly after a while, I get a cross-thread error wich says:
"Cross-thread operation not valid: Control 'ListBox1' accessed from a thread other than the thread it was created on"
Well, where did the ListBox get involved in this problem? The code breaks on this line:
ToolStripStatusLabel3.Text = "Henter data fra eTime-basen..."
So, what am I missing here? I've never encountered this before in any way. I'm only using the ListBox later in my BackgrounWorker, and each time I'm using it I'm checking the InvokeRequired-property to avoid problems with threading.
I have a loop the iterate in my ListBox and I got this error. Cross-thread operation not valid: Control 'ListBox1' accessed from a thread other than the thread it was created on.
Here is my codes:
Private Thread As New System.Threading.Thread(AddressOf myFunc)
Sub myFunc()
Dim i As Integer
[Code]...
My Listbox1 is contain hundreds of lines to loop..thats long iteration. and i need the main form keeps responding from other function even loop is under process. This time i need to use this method of multi-threading.
Im trying to work with threading on a project im doing but i have run into this cross-thread problem, ive worked with background workers before and never had this issue.ive done some searching and found some good threads this one in perticular[URL]..now i tried to use these examples and i made it work on a differant project but i cant seem to get my head around how to make it work on this project.
[Code]...
I have to do a questionaire that gives three questions with multiple choice answers. When the user clicks a radio button it displays a tick or cross depending whether the answer is correct or incorrect. I also want to display, on a label, the number of correct answers with the number of attempts. i.e 1 out of 3. I have listed the code I have for the questions and radio buttons and I know I have to declare form variables but I do not know how to get it to recognise the radio button as a number to add to the total.
Private Sub radBevan_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles radBevan.CheckedChanged
If radBevan.Checked = True Then lblScore.Text = "Incorrect. The answer is Beveridge."
If radBevan.Checked = True Then picTick1.Hide()
If radBevan.Checked = True Then picCross1.Show()
End Sub
I'm going to level with you -- although I heard someone say a long time ago "Never use it"! -- and it stuck with me, if I didn't have this in my form load code, my program wouldn't work.Because, to be completely honest, I could never get my head around the issue regarding the serial port and using delegates. (Haven't given up though).
Anyway, the software works absolutely fine with this statement BUT I get a several errors without it based on that "separate threads" thing (to put it in hillbilly terms). is it still "Never use it"? or am I not alone, and some of you have also used "check for illegal cross threads = false"
I'd like to know what the code is to make a picture box not able to cross a lineshape.
View 3 Replieshow to do serial communication using threading in vb.net 2008,
View 1 RepliesI have an application that requires the use of many threads. How do i monitor the memory consumption of my application?And how can i monitor the CPU usage of my application if possible?And is it possible to monitor the memory consumtion and CPU usage of each of these threads?And is it possible to limit or prioritize the memory consuption or cpu usage of the whole application or of each thread?
View 5 Repliesafter i get a successful ping response i need to send an HTTP request to the device examine the response and then display it. i'm trying to multi thread the 2nd bit with no joy so far.
Imports System.Net
Imports System.Net.NetworkInformation
Imports System.Threading
[code].....
I would like some advice on multi-threading. I currently utilize two threads, one for the GUI, and the other for calculations. This works well, but I want to improve my multi-threading techniques. Currently the data is with the calculation thread, and this occasionally this will cause a slow down. I want to put the data on its own thread. Giving me three threads, Data, UI, and Calculations. This should improve responsiveness, and not be overwhelmingly complex.
My problem is, this no longer fits into the parent child relationship well. All three threads need to interact with each other. My question is, what is the better way of dealing with more than two threads, when all the threads need to interact with each other. Should I pick one thread as the ultimate parent, say the data thread (I pick this one, because it seems to me this thread will be the most free.) Then have the calculation thread and the UI thread children of the data thread. Then when I have a need for the UI thread to explicitly call the calculation thread, I do this through a function in the data thread.