WebBrowser Control - Background And UI Thread Components
Feb 24, 2009
I'm using the webbrowser control in VB.net. I want to click a button and have the webbrowser go to a certain website (done). Then I want it to wait a period of time and then do something on the page its on. The part I'm having a problem with is the waiting period. In the main form I have no problem manipulating controls or anything like that.
One solution would be to use thread.sleep() but that locks the ui and I don't like that. What I am trying to do is have a backgroundworker do the waiting then perform the necessary actions on the webpage, but the backgroundworker isn't able to access that thread, makes sense. I've explored delegates but that doesn't seem to do what I want as it doesn't allow me to put the background thread to sleep before it does its work.
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Sep 23, 2009
Is it possible to create a WebBrowser control in a background thread in BackgroundWorker?
Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
Using web1 As New WebBrowser[code].....
Does anyone know a way to create a background WebBrowser? I would like to do it to extract info from websites then spit out the various HTML DOM arrays
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Feb 24, 2009
I can't seem to find a good tutorial on how to access uithread components from the background thread.. It seems like there is different means of accomplishing this. I'm not picky about which one I use.
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Jul 2, 2011
My application has a total of 1 form. I have several modules, one of which is a module that handles a background worker dynamically. But what I need to be able to do is update a textbox from the background worker thread. Again, this code is contained within a module, not directly on the main form, so I am totally clueless as to how to make a reference to it. It's easy in WinForms, but I can't for the life of me figure out how to do it in WPF...
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Oct 1, 2009
Creates a webbrowser in a background thread, then is supposed to navigate to a url and return a htmldocument, but the navigate fails for some reason
NOTE: this is part of a class where you see ME.url or me. ... me.isrunning = boolean false by default me.url = uri of location to navigate to
Public Function GetDOC(ByVal url As Uri) As HtmlDocument
If Me.IsRunning Then
Throw New Exception("Object Currently In use")
[Code]....
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Apr 22, 2012
I am trying to access a few component using a thread. My form looks like this:
my source looks like this:
Private Sub btnGO_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnGO.Click
pbAction.Value = 0
[Code]....
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Apr 22, 2012
I have a form that looks like this:and i'm using a backgroundworker to update the components:
Code:
Private Sub btnGO_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnGO.Click
[code].....
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Aug 27, 2011
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))
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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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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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Dec 4, 2008
A non-UI thread in my prog needs to obtain data from a UI listview control. To prevent cross-thread errors I use the following, but it freezes the prog (probably because the "Else" part is never called).What am I doing wrong?
[Code]...
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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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Jun 11, 2009
i want to have some web browsers which navigate wile the thread is running and my problem is that I want to use a web browser object from .net in a thread. when i put a webbrowser object in my form, called webbrowser1, i cant reach it in the thread's operation(start thread). when i type webbroeser1 in the thread it doesn't undrestand what webbrowser1 is.
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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 18, 2009
When i run the program i am getting the following error in this line TextBox1.Text &= "File Created: " & FullPath & vbCrLf"Cross-thread operation not valid: Control 'TextBox1' accessed from a thread other than the thread it was created on."
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Sep 5, 2009
I need your help on the following. In debugging mode only the program is stopping to the following line "My.Forms.FormMain.HelpProviderMain.HelpNamespace = "Reports.chm"" with the following error ""An error occurred creating the form. See Exception.InnerException for details. The error is: Cross-thread operation not valid: Control 'FormSplash' accessed from a thread other than the thread it was created on.""
I noticed that when I am putting NONE in SPLASH screen option in the properties of the project, there is no problem.I am no familiar with treating that's why can you give me detail instruction how to overcome this annoying problem?
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Sep 5, 2009
In debugging mode only the program is stopping to the following line "My.Forms.FormMain.HelpProviderMain.HelpNamespace = "Reports.chm""
with the following error ""An error occurred creating the form. See Exception.InnerException for details. The error is: Cross-thread operation not valid: Control 'FormSplash' accessed from a thread other than the thread it was created on.""I noticed that when I am putting NONE in SPLASH screen option in the properties of the project, there is no problem.
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Mar 10, 2010
im getting this error and i cant figure it out.
Public Sub mlogin()
Invoke(chkb, New Object() {"disable"})
Invoke(d, New Object() {achidrtb, "", "="})
Invoke(d, New Object() {hiddenrtb2, "", "="})
[code]....
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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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Mar 25, 2010
I'm using .NET 2.0 Windows Forms and want to add "drawing" components such as lines, rectangles, etc.. I've done this before in MS Access, but I can't seem to find similar things in teh Visual Studio 2005 IDE. Where do I need to look to find these elements?
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Aug 15, 2009
I was wondering if there were any free ribbon controls for vb.net, and if there are not, how I could go about making my own. I don't want to pay $300 or more for a professional one...and I would really like to add one to my project.
What would be the best solution for finding/making one?Here is my google search I tried, I could only find one for c#. If possible, I would like one which is the closest to the one used in Office 2007.
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Feb 15, 2010
My 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
[Code]...
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Jan 26, 2010
I have a program that if user presses a key(while the program isn't focused),it presses some keys(some kind of macro to aid gamers).The program works,but I cannot stop the background thread.I use "t.abort()" (t is the name of background thread) but it keeps working(even when I close all forms) and at TaskManager "keypresser.exe" is still there.[code]
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