VB 2008 - Thread And Listview
Mar 2, 2012
the below code is on a form2..but the listview it must add these items to is on the Form1. I had to use a delegate just to get it to check if a file contains a specific Character. to add 1 to the lables as number of manuals found Everything seems to be be working except it isnt adding items to the lisview, correction. i think everything is working ok and it's not adding items to the listview. I'm trying my best to understand the thread process, but thus far all i get is confusion,when something does'nt work. add items from form2 to a list view in form1 using threading [Code]
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Nov 30, 2009
I'm trying to add information to a ListView from a BackgroundWorker thread. I thought I could do this in this manner:
vb.net
Private Delegate Sub _ListView(ByVal lvi As ListViewItem)
Public Sub test(ByVal lvi As ListViewItem)
[Code].....
When I attempt to run the "test" sub the BackgroundWorker, I get an error:
Argument not specified for parameter 'lvi' of 'Public Syb test(lvi as System.Windows.Forms.ListViewItem)'.
Is there something I need to specify when declaring the sub, or in the sub itself?
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Sep 20, 2009
I'm using the following to check the state of checkboxes and then activate some public subs based on the checked state of the checkboxes:
vb.net
Public Sub TestSub() If Me.CheckBox1.InvokeRequired Then Me. CheckBox1.Invoke(New MethodInvoker(AddressOf TestSub)) Else Begin() End If End Sub
Within the Begin sub, I have code that performs specific actions and then updates a ListView with that information.As far as I can tell, the actions are being performed, but the ListView isn't being updated with the info.I'm calling the Test sub from a seperate form, within the BackGroundWorker's DoWork event.Would I have to check the InvokeRequired property of the ListView as well?I'm looking more into the documentation of the BackGroundWorker.
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Oct 3, 2009
[Code] If I wanted to add 3 icons, the LV would add them like it normally would, but then, for some reason, it enters the loop again and that's when it throws this error: ex = {"Cross-thread operation not valid: Control 'ListView1' accessed from a thread other than the thread it was created on."}. I don't understand why, because I'm invoking the LV.
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Jan 22, 2012
cedure that populates a ListView, but it does a lot of work and it takes too much time to display all it's items (about 100-200 items). I want to use a thread to display the items as it's extracting data (real-time).I posted a question earlier here, but using a ListView it's not working for me...
Imports System.Threading
Imports System.ComponentModel
Public Class Form1
[code].....
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Aug 5, 2010
I am writing a basic application to provide remote support to multiple computers over a TCP Stream. For example, if my brother/dad has an issue with their computer, rather than going over to help them I can just use remote support (Yes, I know Windows has Remove Desktop, and their is TeamViewer, ect. But where is the fun in using those =P)Anyway, it basically works by taking a PrintScreen of their computer, sending it to mine and displaying it in a PictureBox, then when I click the image, it records the coordinates of my mouse, sends it to theirs (Little Maths for resolutions and positions ofc) and clicks, then sends a new image.
My problem is, I want a ListView displaying the PC Info, like:
PCName - RAM - Free HDD Space - 32/64Bit - Processor Speed
Now, my problem is, I have a Class which does the TCP Server, and in that class when it Receives a Message, it calls the Sub "RunCommand(ByVal Command As String)", which then splits the String and works with it.So, for example, their PC would send the String "Info|DadPC|2GB|235GB|32Bit|2.2GhZ|" And mine would split it, and add that data accordingly.However, what happens is, nothing. If I put in "MsgBox()" anywhere in the Code, it shows it is all Split, and received correctly and everything is fine, but no matter what happens, it wont add to the ListView (Or anywhere else on the form, for example "GUI.Text = Info(1)" Wont work either)?
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Apr 19, 2010
Would someone mind explaining to me how visual basic treats a ListView object? It seems that if I create a new ListView and make it equal to the old ListView it's like filling the new ListView "ByRef" so to speak.
I'm running into problems because of this when I try to do some processing with the selected items in a new thread. Does anyone have a better solution to this than using a delegate to call a fucntion which populates an ArrayList with the ListView.SelectedItems and then returns the ArrayList?
Edit: Seems no-one is answering well let me ask a "hopefully" easier sub-question.
If i'm trying to pass a ListView into my BackgroundWorker as an argument, how do I successfully do that? I've heard someone say "make a copy". Yet I still get cross thread exceptions on my e.Argument. Tips, tricks, musings, all very welcome.
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Mar 22, 2010
Im trying to do this
[Code]...
But it will just skip to the last status (Label3.Text = "Status: Welcome")
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Jun 10, 2010
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).
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Aug 16, 2011
I've got an application with a ListView and I want to loop through each item in the ListView. But I want to do this in a separate thread.
This is a very simple version of the code - but its error is the same:
Private Sub StartToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles StartToolStripMenuItem.Click
pingThread = New Thread(AddressOf loopingRoutine)
[Code].....
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Jan 22, 2012
I have a procedure that populates a ListView, but it does a lot of work and it takes too much time to display all it's items (about 100-200 items). I want to use a thread to display the items as it's extracting data (real-time).
[Code]...
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Feb 21, 2011
I am trying to add a subitem to a listview in a threadsafe manner.In a single threaded application it works like so:
[Code]...
However if run in another thread it causes a cross threading error.I have looked at examples of delegate subs that use Invoke, but all examples i have seen involve updating the text property of an object, and i cant get my head round how to apply the concept to actually add a subitem to a listview.
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Jan 26, 2010
For some reason, the following code is causing me some issues. This code pulls lockout status data from AD and contains the data within a datatable. An event is raised from the threaded procedure to add the data to a listview control. For some reason one row of data gets added to the listview control and when you run the procedure gain, 2 rows of the same data gets added, and then 3 rows, etc.
This code calls the procedure "CallGetUserLockout"
GetLockoutStatusToolStripMenuItem.DropDownItems.Add("For Current User - " & User, Nothing, AddressOf CallGetUserLockout)
[code].....
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Sep 16, 2009
I currently have a form with a listview. On another form, I would like get all the items from that listview. This I can achieve but I always get the "Cross-Thread operation not allowed exception" message. I've tried the following code to avail.
[Code]...
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Oct 7, 2010
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).
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Feb 22, 2011
I have a small program that checks webpages for certain strings. I am using VB express 2010 .net version 4.I have the list of URLs in a listview, and loop through all the urls, perform a webrequest, check if the source contains certain strings and then add a subitem to the current listview with text to indicate the result I am attempting to speed the application up using a parallel.for loop, but this causes a cross threading exception.This is the code for single threaded:
For i As Integer = 0 to lvUrls.Items.Count - 1
Dim lv As ListViewItem = lvUrls.Items(i)
lv.UseItemStyleForSubItems = False
[code]....
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Aug 13, 2010
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".
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Nov 3, 2011
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.
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Jul 21, 2009
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.)
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Jun 21, 2012
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
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Feb 17, 2012
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]...
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Sep 2, 2010
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).
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Jun 6, 2010
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.
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Feb 9, 2011
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]...
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Apr 1, 2010
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]....
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Jun 6, 2009
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
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Aug 4, 2009
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]....
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Feb 7, 2011
Ok i have a Form with the following
Private Sub frmMain_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
txtNotepad.Text = LoadFile("notes.txt")
[code].....
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Sep 22, 2009
I have a vb-2008 program that contains a (listview) control.
View = details
AllowColumnReorder = true
Lets say the table has 3 columns (a,b,c) and 1 row of data.
a b c
1 2 3
I want the user to be able to re-arrange the columns (by dragging the column headers) before printing the contents of the table.
c a b
3 1 2
Statements like:
.. ListViewX.Columns(2).Text
.. ListViewX.Columns.Item(2).Text
.. ListViewX.Items(0).SubItems(2).ToString
Give the column-name (c) and cell-contents (3) of the origional table .. not the (3rd) column (b) of the re-arranged table.
How can i get the column-name and cell-contents of the (3rd) column of the re-arranged table?
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Mar 21, 2010
Do I really have to go through all this just to find out what item has been selected in a ListView?
[Code]...
Isn't there something fundamental like this? Is absolutely everything in VB.NET buried beneath a colossal heap of bureaucracy?
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