VS 2008 Accessing A Flexgrid From Another Thread?
Aug 14, 2009
I�m having trouble accessing a flexgrid from a different thread.Basically in my main mdiParent I have some code like this, this code is triddered when the aplication receives a message from a remote client
Public Delegate Sub UpdateActionsGridStatusDelegate()
Me.Invoke(New UpdateActionsGridStatusDelegate(AddressOf frmActions.UpdateActionsGridStatus))
I also have a form called frmActions, which contains the function �UpdateActionsGridStatus�
Public Sub UpdateActionsGridStatus()
MsgBox("Actions row cnt = " & Me.flxActions.Rows.Count - 1)
End sub
If I run it from a button on the flxActions form it works fine.When I run this function from a thread it returns 0 rows!
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Jul 13, 2010
In my program (PassGen) i have a DataGridView control that stores passwords.But when i add more about 20,000 or more entries at the same time (using "Generate List", UI freezes up for a few minutes.I tried to add new entries from a background thread (so main thread will redraw the form), but run into exceptions How to do that?
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Sep 8, 2009
I have a form with Check Boxes on it and a second form that holds functions and a Backgroundworker.When a button is pressed on the first form, the second form loads and then runs the functions that relate to the appropriate Check Boxes.Doing it this way causes the second form to become inaccessible. I decided to run my code in the Backgroundworker's DoWork event and then call the RunWorkerAsync method in my form's Activated event. Before using the Backgroundworker, everything worked fine and now it doesn't.I assume the issue is with the Backgroundworker not being able to access controls on another thread.In debug mode,it automatically throws an exception, but doesn't error out when using the Release version, making me assume it's a legal call. But, if it's a legal call, then why can't I access the controls?
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Oct 11, 2011
As we know, one STA UI thread creats the controls only canbe accessed in the UI thread in Winform application. And we need to call control.invoke or begininvoke to run the code in the background thread.
Yes, below code in VB.Net , VS 2010 Winform project can throw the exception "Cross-thread operation not valid: Control 'Form1' accessed from a thread other than the thread it was created on."
[Code]...
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Oct 6, 2011
how to add a row on a flexgrid because i have a new table that i created and the table has nothing on it.
[Code]...
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Oct 21, 2011
I am using webbrowser control to parse html.I used to have this code that works just fine
vb.net
Public Shared Sub putHtmlIntoWebBrowser(ByVal html As String)
'WebBrowser.DocumentText = html
[code].....
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Jul 5, 2011
I have a function that is called when a file is modified in a folder. This function updates the items of a listview which is stored in the UI.Here is the function :
Private Sub FileChangeNotify()
Try
LstMoulures.Items.Refresh()
[code]....
Here is the error: "Le thread appelant ne peut pas accéder à cet objet parce qu'un autre thread en est propriétaire." (Translation : The calling thread cannot access this object because it is owned by another thread)
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Feb 1, 2011
ccessing a UI object with a Thread gives an error
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Sep 26, 2011
I have an exceptionhandler function that basically just writes a line to a textbox on Form1. This works fine when being run normally but the second I use a thread to start a process it cannot access the property. No exception is thrown but no text is written to the textbox:
Public Sub ExceptionHandler(ByVal Description As String, Optional ByVal Message As String = Nothing)
' Add Error To Textbox
If Message = Nothing Then
Form1.txtErrLog.Text += Description & vbCrLf
Log_Error(Description)
[Code] .....
Is it possible to access a form's properties from a thread this way or would it be easier to write to a text file or similar and refresh the textbox properties every 10 seconds or so (Don't see this as a good option but if it's the only way it will have to do!).
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Apr 16, 2011
im trying to access a richtextbox from another class and thread then the ui and i cant seem to get it working. I currently have the sub thats handling the the work inside of a public class and its a sharedsub, im going to be calling it from several different classes and threads but again i cant seem to get it working. the code looks like this. Public Class SharedSubs
[code]...
i would be calling sub using SharedSubs.Console("stringstring") when this is called from the ui thread it works fine but when its called from anyother thread or class its does nothing,ive confirmed it going thru this code but its not displaying anything in the textbox and its not thru an exception due to delegates either which i figured it would.
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Jul 21, 2011
I'm trying to update a dependancy property in VB.Net 4.0 inside of an Async callback. I feel like I am doing this correctly but I'm still getting the "The calling thread cannot access this object because a different thread owns it." error. Does someone see a better way of using delegates in VB.Net 4.0?
Private WithEvents myObj as CallingObject
Private Delegate Sub MyErrorDel(ByVal strError as string)
Public Property ErrorMessage As String
[code]....
Whenever ErrorMessage gets set inside of DisplayError an exception gets thrown, even though I am using the dispatcher to call DisplayError.
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Aug 25, 2009
how to access the main ui's labels from a delegate method?
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Jan 5, 2012
Im having a problem understanding if accessing httpcontext inside a shared function, without passing in the httpcontext as a parameter is thread safe?
Are the 2 functions in the util class equally thread safe?
Class foo
Sub main()
Dim qs1 = util.getQS(HttpContext.Current)
[Code]....
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Nov 14, 2011
It appears that when you access My.Settings.Default in VB.NET, your thread's CurrentPrincipal changes. Consider the following code.
[Code]...
Is this expected? Is it documented anywhere? I couldn't find any references to it.It also seems to only do this the first time My.MySettings.Default is accessed, which means that a workaround might be to touch the property to initialize it before attempting to set the thread's CurrentPrincipal. Would there be any undesirable side effects to doing that?
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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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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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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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Sep 8, 2010
I am Using VB.NET 08 code for Creating FlexGrid Control.Now i am showing the data table in the FlexGrid.But now i want to put a Button Control on the FlexGrid Cells.The Button acts like When i click button some of the Rows in the Flexgrid should be Hide/UnHide.So how can i write a code for Creating control on the Flexgrid and applay the above criteria?
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Nov 14, 2011
I'm in the process of rewriting some old VB6 projects in VB.Net which are still in use in my office. One project I'm having trouble with is one that displays a flexigrid which contains data from an SQL database, I know I can use Datagridview and this will fill most of my needs, but there is one characteristic of the flexigrid is the ability to "freeze" the far left column which hold peoples names and scroll all the other columns to see the data to the left, is there a way I can get Datagridview to do the same?
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