C# - Control.Invoke Error: Handle Not Yet Created?
Jan 31, 2012
I show a waiting form (saying "Please wait...") on a different thread when there is long-running code in some forms (for example, during data loading). I show the form like this:
m_PopProcessingThread = New Thread(New ThreadStart(
Sub()
m_PopProcessingForm = New WaitingForm(m_Message)
Application.Run(m_PopProcessingForm)
End Sub))
[Code]...
The stack trace points to the part of code where I hide the form. How could the handle not have been created, when just before the Invoke call, I loop until said handle is created?
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Aug 27, 2010
I have a filesystewatcher object. On it`s event it runs a procedure which fills a treeview with a data. I had problems with treeview methods, but when I run them using invoke method everything is ok. But I still have one problem. When I load the form for the first time, everything works fine. But, when I then close the form (me.dispose, me.close), and load it once again, when Filesystemwathcer start the procedure i have an exception "invoke or begininvoke cannot be called on a control until the window handle has been created" trying to run a treeview.invoke method?
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Mar 5, 2009
i AM TRYING TO USE A THREAD TO UPDATE SOME CONTROL during runtime using invoke and i get this message.here is my scenario:im trying to build a performance monitor tooli have a mainform that is MDI parent and i create mdi child using
[Code]...
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Sep 29, 2009
I am developing an application which created a series of labels using code such as this below[code]...
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Mar 16, 2010
I've got the following code:
[code]...
The problem is that, when I call the "SetStatusBarText" sub from another thread, InvokeRequired is True (as it should be), but then my threads stall on the Me.Invoke statement - pausing execution shows them all just sitting there, not actually invoking anything.
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Dec 6, 2011
I'm trying to add subs that will handle MouseOver events on textboxes that don't get created until after the program starts.
Each textbox gets created with a unique number attached to it like this...
AptTextBox0
AptTextBox1
AptTextBox2
etc...
Depending on how many are needed. But I never expect more than say... 15 at any given time.
Is it possible to handle MouseOver (or any events for that matter) if they don't exist until later.
I tried this but it didn't work....
I added this is the Designer code....
Friend WithEvents AptTextBox0 As System.Windows.Forms.TextBox
Friend WithEvents AptTextBox1 As System.Windows.Forms.TextBox
Friend WithEvents AptTextBox2 As System.Windows.Forms.TextBox
[Code]....
But it doesn't do anything. I don't get errors, but apparently it's still missing something to properly handle the events.
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Aug 19, 2010
Handle EventArgs on Variable or Not Yet Created Controls
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Jan 10, 2012
I have created a PictureBox array to hold 104 playing cards that are all visible at the same time.I did this with this line in the declarations:Shared Card(104) As PictureBox
And with these lines in the Form_Load module:
For I% = 1 To 104
Card(I%) = New PictureBox
Card(I%).Name = String.Format("Card{0}", I%.ToString)
Card(I%).Size = New Size(71, 96)
[Code]...
I have been successful in creating the array, positioning each and entering the images for all 104 PictureBoxes, but now I want to add code for the event "MouseDown.I copied the code for this event from my VB3 program and VB10 automatically updated the list of parameters, but nothing has linked the objects (Card) to the code.
I have tried to append "Handles Card.MouseDown" as well as several variations with brackets to indicate that it is an array.Auto-complete doesn't include "Card" as an option, and of course, since the array was never an object added to the form design, I can't create the empty module from there.
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Aug 20, 2009
1. On the main form a scanner class is instantiated that (in the scanner's constructor) sets the scanner settings (baud rate, parity, etc) and opens the scanner for use
2. A barcode is scanned (via a scanner connected to the device in a seral port) while on the main form
3. In the scanner class, the DataRecieved event gets the needed info from the scanned code.
4. Then that info is passed back to the main form to a method RunCommandCode (which takes the scanned info as an argument)
5. On the main form the RunCommandCode calls another method CommandCodeHandler, passing the scanned info again
6. In the CommandCodeHandler sub a method is called in a Utils class (SetSelectedTab), which interacts with the form itself (determines how many tabs exist on a tab control), which is the reason for the invoke in the first place
So, before I figured out I needed to use the Invoke method (and, more specifically, that the scanner was working in a different thread), I was getting an error in step 6 on the line that got the TabControl.TabPages.Count.
[code]...
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Oct 1, 2009
I'm working with the DevExpress XtraGrid control.I have a routine that goes thru and adds all the controls on the current form dynamically, and launches on a seperate thread the routine for a given control to initialize it to the value that will be displayed to the end-user. Some of the controls are displaying calculated values, and take some time to return their values, so that's why we are doing it on a seperate thread.
[Code]...
I'm using a similar snippet of code for any control properties that have to be updated, and all work fine. On the above code when the actual Invoke is called, it APPEARS that the thread just ends and never calls the delegate, and doesn't return to finish either.
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Nov 16, 2010
I have an annoying bug which is very difficult to replicate. When I start my application, from time to time, I get this error message "Invoke or BeginInvoke cannot be called on a control until the window handle has been created". This makes the user think the application is unstable... I have no idea what could cause this problem. The application uses a splash screen. It's built in Visual Basic using VS 2010 and .net framework 4.
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Oct 6, 2010
how to invoke methods, but how does one change a simple property?
For demonstration-sake, here's a very simple set of code that should help. Let's say I need to set the visible property from a child form, and thus, it needs to be invoked:
Friend Sub activateItem(ByVal myItem As PictureBox)
If myItem.InvokeRequired = True Then
????
[Code]....
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May 13, 2009
i'am trying to open the autocomplete-window from a textbox without typing chars into the box.Normaly the autocompletewindow opens only if you type in a character, but this means, you have to know the first char.Is there any way to open the autocompletewindow without the first character? For example at the mouseover event of the textbox?
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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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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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Nov 9, 2009
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]....
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Nov 10, 2005
I'm currently invoking a function that takes ByRef parameters using Control.Invoke (which I notice specifies the Object parameter array to be ByVal) but the array of parameters I give it isn't updated by the function. Is this possible with VB.Net 2003 or must there be some error in my code?
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Aug 19, 2010
This is the code i have so far (no i didn't write it all by my self took help from net) but i am unable to understand why i am getting this error
Imports CookComputing.XmlRpc
Public Structure blogInfo
Public title As String
[code]....
error i get is "Invoke on Non-Existent or Non-public proxy method"
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Apr 2, 2010
My application produces this error System.Data.SqlClient.SqlException: Login failed for user..This started after I added a stored proc in my dbml file. It works fine in my local enviroment, but throws that error when deploy to staging sever. the user it displays is foreign to me?
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Dec 8, 2009
I have the following Stored Procedures create or replace PROCEDURE WEB_AC
[Code]...
First one: At some point in the application I have the valor parameter (of the visual Basic Function) as a string with spaces that is something like "some string with spaces". When this happens, the stored procedure don't update the table. If I execute the SP directly in the DB (with SQL Developer) all works fine. I know it has something to do with the string missing some quotes(') but I haven't make it work yet. Some ideas on this?
Second problem: Sometimes, when debuging the application, if I interrupt the execution, I start getting the ORA-24338 'statement handle not executed' error for hours every time I try to execute it again. I believe it has something to do with an open transaction. But honestly, as I'm new in working with Oracle, I really have no idea what the problem could be.
[Code]...
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Feb 24, 2012
I've looked throu all of the SendMessage(messages) but there does not seem to be anything like WM_GetPos.Now I can accomplish through AHK with ControlGetPos, but for the life of me I can not figure out what Win API function they are calling to accomplish this.We have an order entry system we use, that I am trying to automate the printing of our reports (we have 4 per order form) to save time
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Jul 16, 2009
I have an application that dynamically creates winforms.
Dim NewS As New Form
Dim NewT as new Timer
NewT.Interval = 5000
[Code].....
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Apr 10, 2009
What is Platform Invoke Service (P/Invoke)?
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Oct 13, 2010
We have a UI with a progressbar. I know how to invoke, safely, the control from which it was not created from a thread. there are threads being processed in a threadpool, all of which calls an "agent" (which is a notifier to raise an event back to the UI to then increase the progressbar). an "agent" is set as a property in a State object, which is then passed into a method which will be executed on the ThreadPool. so, I invoke on the UI the method to update the progressbar, but the bar does not seem to update at all (screen frozen) and it takes a very very long time for it to execute. without threading, no problem.
[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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Aug 15, 2009
I am adding some controls to a panel at run-time. After I add them I need to loop through the panel in a different sub and test for a specific control. I was assuming that if I named the variable that the control is set to to "a", that I could then test for this by saying
[Code]...
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May 8, 2009
I need the intPtr for a form. Control.FromHandle(control) gives me the control from a handle, but I need the opposite--get the handle from a control. How do I do this?
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Apr 27, 2009
I need to get the handle of a control as an IntPtr to pass to a screen capture class in vb.Net 3.0. Tried this but get an invalid handle exception.
Dim hwnd As IntPtr = Runtime.InteropServices.GCHandle.Alloc(CanvasMap)
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Jul 16, 2009
I have an application that dynamically creates winforms.
Dim NewS As New Form
Dim NewT as new Timer
NewT.Interval = 5000
[code]......
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