Multitasking Interacting With UI Thread?
Oct 1, 2011
I'm trying to start to use the Task class for multi-threading. This is a really simple example so I can work out the ins and outs. As an example, I have the below thread, the thread.sleep is used to represent large amounts of data processing, at the end of which I'd like to update something on the screen. Please advise a good way to achieve the idea of the below code with respect to the text box update.
With the old threading system, I would grab the UI context, and do a .post/.send to it. I'd like to have that ability with the newer task system, but am open to the preferred way of solving this.
As a back ground, the threads I will be replacing were previously constantly running during the app with a do/while that was killed at app close.
[Code]...
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Nov 15, 2009
I have a method that is asynchronously called when System.Net.Sockets.NetworkStream.BeginRead completes.
skDelegate = New AsyncCallback(AddressOf skDataReceived)
skStream.BeginRead(skBuffer, 0, 100000, skDelegate, New Object)
In that callback method, I need to interact with the UI thread.
Sub skDataReceived(ByVal result As IAsyncResult)
CType(My.Application.OpenForms.Item("frmMain"), frmMain).refreshStats(d1, d2)
End Sub
This causes an exception after the method completes. (when End Sub is executed)
[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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Jul 10, 2010
I searched around the web for some tutorials and code examples, but couldn't find anything up to date. For example if i wanted to hit the "+" button on the windows calculator using an application i made what would be the best route to do so?
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Apr 15, 2012
I am lookin for source from where i can learn to change control properties at runtime using VB.NET. Actually I havent started working on the project so I cant mention exactly what I need.
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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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Mar 17, 2009
I have a project in Visual Basic 2008 where there is a Main Class and couple of classes inside the Main Class. I want to be able to share variables/objects within the Main Class and SubClasses while those vars/object are instanced.
Ex:
Code:
Public Class clsMain
Public t as New clsSub1
[Code].....
So, can i make var1 be in separate instances per clsMain in the memory while being able to access the var1 in clsSub1?
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Nov 16, 2010
I am trying to have a ComboBox on my form, be able to change the selected item in a Listbox/Combobox on a website, through a webbrowser control.
For instance, here is the HTML coding I am trying to interact with on the webpage:
<select name="day">
<option>1</option><option>2</option><option>3</option><option>4</option><option>5</option><option>6</option><option>7</option><option>8</option>
[Code].....
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Mar 12, 2009
I want to be able to make Internet Explorer navigate to the "about:blank" page every time its user navigates to a wesite that is blocked by the HOSTS file. Does anyone know the code that I can use to do this?
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Oct 10, 2009
What classes has vb.net got to work with video files...like mpg or mp4i wanna write some code to be able to save a specific video frame to a jpg image.
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May 11, 2012
I have a MDI parent on which i launch a child form
Dim NewMDIChild As New Frm_addOT
'Set the Parent Form of the Child window.
NewMDIChild.MdiParent = Me
'Display the new form.
NewMDIChild.Show()
His child form contains several comboboxes which hold data from a dbase(sql)
When new data is entered in the cmb it checks the database and if it isn't in there it launches another window
FRM_OTlistaddklant.Visible = True
and copy's the newly entered text in a textbox.
FRM_OTlistaddklant.TB_klantnaam.Text = OTaddklant_naam
then i can give in the details etc.
now, when this is done and the users presses a button "Add"
the information is written to sql(which works perfect)
than i have a public sub on the Frm_addOT which should refill the combobox and
also set the backcolor to a specific color.
and the last two things will not work. Actually when i try to change the backcolor on Frm_addot it triggers the event backcolorchanged and says it has changed but it is not visible.
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Apr 3, 2011
I want to make a usercontrol that I can then use on my project form, and then interact with it. (for example, get the result of a calculation that was made in the user control and then make futher calculations on my form) I basicly know how to make a Usercontrol, by not how to use the information that it derives for further use.
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Jul 2, 2009
I just wondered if it was possable to say load a webpage then press a button on a certan webpage?
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Apr 26, 2012
I am using VB.NET to automate a web form submission using SHDocVw.InternetExplorer. I have navigated to the form, filled in all of the fields successfully, and clicked the update button. By design the web application then opens a JavaScript SubModal window in the center of the screen. It looks like a "floating iframe" for lack of a better description. [code]I need to find a reliable way (i.e Not SendKeys). to get the HTML source of this popup in order to click a button.
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Feb 24, 2011
I am writing (and teaching myself how to write) an experimental assembly in VB.NET 3.5 that is exposed via COM and then called from some Excel VBA code to initiate an instance of a class that traps some Excel events and then perform some functions on the active workbook in Excel.To initiate the class, a reference to the Excel Application is passed from the VBA (I am using a PIA for Excel in the assembly).I needed to perform a time-consuming operation on the active workbook from my assembly so I decided to use a BackgroundWorker in a WinForm so that I can display a progress dialog for the operation whilst the operation completes in the background.
I would like to know if there are any problems with interacting with Excel via COM using a background worker in this way? Reason for asking is that the main class in the assembly holds the reference to the Excel application object, and this is then passed to the BackgroundWorker so that it can determine the active workbook and then perform some operations on it. I am only accessing the workbook itself (not other objects) through one procedure.
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Feb 27, 2011
following error as I am unable to find a fix:Description:A problem caused this program to stop interacting with Windows.
[Code]...
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Jan 9, 2010
I didn't know where to post this question so I hope I put it in the right forum...I am not new to Visual Basic, however I am definitely not an advanced user. I would like to build an application that would allow me to interact with other programs on my computer. For example, if I were to build an application that could control iTunes, how would I go about this?
Or, I am looking to make an application that would allow me to do little things on my computer like disable my track pad if I have a mouse plugged in. How would I build something that could interact with windows (or iTunes) like that?
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Jul 23, 2009
I have a windows form that I would like to have search for an html button in the user's browser. I would need the location of the button on the screen.
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Jul 19, 2010
I have a windows form that I would like to have search for an html button in the user's browser. I would need the location of the button on the screen
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Nov 9, 2011
If only there were an easier way of traversing ASP.NET controls in the codebehind. This has been the bane of my existence as an interning .NET developer. entifying the proper member of the ListView controls. I've deleted all the presentation code in the markup to make it easier to look, since it isn't relevant anyway. Here's the situation:Markup
<asp:ListView ID="NewProduct" runat="server" DataSourceID="NewProductSDS" DataKeyNames="ID">
<ItemTemplate>
[code].....
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