Error Creating Window Handle In A Thread?
Sep 14, 2011
I've a little program that has got tabControl with 2 tabs - "results" and "log". My idea was that when an error occurs the tab will switch automatically on tbLog to show what the problem was. Most arguably the problem is in threading. This is the code that..I use:
Dim thread As New Thread(AddressOf ExecuteQuery)
thread.Start()
ExecuteQuery executes the query and I'm making an error deliberately to see if I'll be automatically switched to the log tab which is in Try-EndTry procedure:
tbGrid.SelectedTab = tbGrid.TabPages(1)
The program indeed switches to tabLog (which is number 1) but I don't see any controls on it (txtLog), then when I'm trying to switch tabs a couple of times I get "Error creating window handle in a thread". I read other forum threads about it where people as how many controls do they have in their programs but my program does not exceed 70 controls on a form.
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May 21, 2010
There are three forms on this application and they are a MDI Frame(frmMain) and two child forms (frmSearchEmp, frmEmpDetail).
What I am trying to do is opening a "frmEmpDetail" by executing "CallEmpDetail()" on "frmSearchEmp".[code]....
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Sep 3, 2009
I am using a Thread object to perform a function. This function performs a task and displays its progress in the gridview (like adding rows changing text etc )
The reason I am using a thread for this function is that there is a cancel button on the form. While the task is in progress, user can click on cancel to abort it.
Private Sub BtnStart_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnStart.Click m_Thread = New System.Threading.Thread(AddressOf myfunction) m_Thread.Start() End Sub
The function works fine and thread is completed. But calling any method of datagridview after thread is completed ( outside the worker thread ) generates an error- "Error creating window handle".
That's probably because i am not using the invoke method of datagridview for calling its methods or readingwriting properties Do i have to create separate delegates for all the methods properties used in the function ( worker thread)
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Jul 14, 2012
I'm in the process of converting a VB6.0 application to VB.Net (2008 Express). I have a MDI parent form, I'll call mdiBackground, and 4 MDI child forms, frmStatus, frmShow, frmQwerty, and frmSentence.The layout is as follows:mdibackground - has the menus at top and is a container for the child forms.frmSentence - appears at the top frmShow & frmQwerty - appear at the left and when one is closed the other one is in the same position.frmStatus - appears at the right, it has buttons which control when frmShow and frmQwerty are to appear I have a couple of regular forms that act as dialog forms. The Me.Close() works fine on these.
[Code]...
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Jan 10, 2012
We have a VB 2008 Windows application that is deployed on several hundred computers. For some strange reason only 2 computers out of the hundreds are experiencing the "Error creating Window handle" error. It is happening more consistantly on one machine than the other. Any idea what might be causing annoying error on such a limited basis? (It's a Windows XP machine that it is happening on. That's all the info I know regarding the machine currently.)
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Aug 4, 2010
unhandled exception has occurred in your application. if you click continue, the application will ignorethis error and attempt continue. If you click quit, the application will close immediately"error creating window handle"What is this and how do I get rid of it?
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Aug 23, 2009
In vb.net and made a proj. in vb2005. but when i try to load a particular form(opens up in a mdi container like all others in the project) , an error-error creating windows handle pops up, the line is frmadmn(the form).show
What shall i do? i read a lil on the net about too many handles, user objects etc. but the stats of my proj. at the time of error are-handles-350,threads-17,user objects-235 gdi objects - 159. have these anything to do with the prob.. then what should i do..? i read about the dispose command also about how to use it ? what to dispose...?
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Aug 27, 2010
I get this error as below when I open my "frmAddPrivate" more than 5 times. How I can overcome it?
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Dec 6, 2008
I'm currently developing a little hobby project to display health information in a game on my G15 keyboard through VB.NET. When I use ReadProcessMemory via an API call, it keeps returning zero. The MSDN documentation referred me to use the Marshal.GetLastWin32Error() call to find out what is wrong and it returns 1400: INVALID WINDOW HANDLE.
I am now confused about whether the first argument of the function wants a window handle or a process id. Regardless, I have tried both with FindWindow and hardcoding the process id while the application is running (getting it from task manager). I have tried three different games, Urban Terror, Grand Theft Auto: SA and 3D pinball for windows, getting the memory addresses from an application called Cheat Engine; they all seem to fail. [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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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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Mar 20, 2010
I am trying to find the handle of the child window for the Yes button in the User Account Control window so i can click it. This window has a structure with a few child windows with the same name.
Dim hwnd As IntPtr = FindWindow(Nothing, "User Account Control")
Dim hwnd2 As IntPtr = FindWindowEx(hwnd, 0, "DirectUIHWND", vbNullString)
Dim hwnd3 As IntPtr = FindWindowEx(hwnd2, 0, "CtrlNotifySink", vbNullString)
Dim hwnd4 As IntPtr = FindWindowEx(hwnd3, 0, "Button", "&Yes")
There are multiple CtrNotifySink with its own Button child window or other child windows. How do i search thru the different CtrNotifySink window to find the one that contain the Yes button so i can send a click to it? I do need to find it before i can send a click, right? because i try just sending it to the main window with sendmessage and nothing happen.I even try sending it directly to the handle found by spy++ of the yes button with bm click but nothing happen?
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Nov 12, 2009
Preface: I know this is an unusual/improper way to do this. I can do this with a "real" ShowDialog(), background worker/thread, and so on. I am trying to do specifically what I describe here, even if it is ugly. If this is impossible for X reason, I have created a fancy progress dialog for some of our long running operations. I need to have this dialog shown on a new thread while having processing continue on the calling (UI in most cases) thread.
[Code]...
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Aug 21, 2010
How can I get the handle of the window that is below (or behind, whatever you call it) the foreground window?
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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 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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Jan 22, 2011
I've got a form that acts as a progress report for a long running operation, it has a listview on it (which I might be replacing with a DGV soon) that gets updated with progress updates from a background thread that is doing all the work. The method running on the background thread raises events that the form then handles and adds the string passed in to this event to the listview. The method running on the background thread raises progress update events several times a second and for each of these updates the event handler on the form must invoke a method on the UI thread to actually add the item to the listview.
This works fine on my test PC (which has a quad core CPU and 8 GB of RAM) but others have reported that after a while the form goes to the Not Responding state so I'm assuming all of these updates on the UI thread are being requested too often for it to be able to process them all as well as user input.So I'm looking for a better solution and have come up with the following:When the background thread raises these progress updated events, instead of them being added to the listview instantly I add them to a Queue(Of String). Then every second the form would check this queue and remove any items currently in it and add them to the listview - using a Queue(Of T) instead of a List(Of T) should guarantee they come out in the correct order. Both of these operations (adding to the queue and reading/removing from it) would be done under a SyncLock block that would lock on the same object to avoid both threads trying to work with the queue at the same time, so there would still be some contention but I'm hoping it would mean the UI thread only gets busy once a second instead of potentially roughly 30 times a second as it is doing now.Does that sound like a good plan? Can anyone think of a better way of handling this?
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Apr 7, 2011
I am in the planning stages for developing a VB.Net class (let's call it OpDAq) that is to obtain data via an API provided by a COM object (AxInterop.TWSLib) that makes requests to an Internet server. The API provides data via events. Class OpDAq should do its work on a separate thread; it takes several seconds (sometimes up to ~10) to collect the desired data. One should be able to create several instances of OpDAq in order to collect data in parallel. The class would be given a reference to the TWSLib object when its constructor is called, as well as several parameters. There needs to be a way for the class to provide results, preferably in the form of a generic list.
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Feb 5, 2011
I have an application which runs two threads.
- One thread is the main thread while the other one is to monitor the main thread.
- The errors are written to a custom event log
- There is an event handler to handle the event logs
- When an event occurs I want to create a new thread and update the event to a sql table (pseudo code)
- Also in case their are number of errors/events
how should I handle them (pseudo code)
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Jun 6, 2011
I am in a trouble with this error:"An attempt has been made to free an RCW that is in use. The RCW is in use on the active thread or another thread. Attempting to free an in-use RCW can cause corruption or data loss." I am not sure if the RCW-error is related to my problem but I was having this error last January 25. It appears when I am ending my application. I ignored it. The next morning when I resumed coding for my application, the changes I am making does not appear at run-time anymore. Whatever GUI changes I make in my application (at design time), it does not make any effect any longer when I am running the application. What is causing this? I am so afraid if I have to restart my application from the scratch. I have gone far.
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Nov 25, 2011
I have am using a Twitter streaming class library, and would like to update a listbox when a new tweet is posted. I have it all set up to the point where a message box will show when a tweet comes in, but when I try to insert this tweet into a listbox I get this error: The calling thread cannot access this object because a different thread owns it. I don't know what I need to do in order to insert this tweet.
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May 20, 2009
I am trying to get the handle of a window to get it's title text. I tried the WindowFromPoint, but it will get any control, not just a window. How do I get the window that the mouse is over?
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Apr 27, 2011
If you open several FullTilt games table, you can see that when on a table is required action it jumps automatically in foreground, BUT WITHOUT TO BE ACTIVATED, so that it title bar is grey and not blue. The window is the top window for my eyes, but it is not active.Now the question is: how to get the Hwnd of the topt VISIBLE desktop window (the window that is over all the other windows), also if it is not the active window?I can't use the GetForegroundWindow Api, becouse it gives the Hwnd of the top ACTIVE window...
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Aug 22, 2010
I have a handle to a window using the FindWindowA() function in the User32.dll (Windows API) and I would to get focus on that window at a later time in my program. how to do that with either a .NET function or User32.dll function? Is there a totally .NET way to get the window handle and focus?
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Mar 1, 2012
<DllImport("user32.dll", SetLastError:=True)> _
Private Shared Function SetActiveWindow(ByVal hWnd As IntPtr) As IntPtr
End Function
[Code]......
I'm trying to make use of some functionality from an external app in my program.
My problem is this:
My program manages to start the external app correctly and I can even get the WinHandle correctly if I don't use "ProcessWindowStyle.Minimized" when starting the app.
If I start the app minimized, WinHandle = ProcID.MainWindowHandle returns a 0 and as I understand it, it's
because the app is hidden in the system tray.
How can I start the app minimized and then get the window's handle once it has been minimized?
I've tried various functions like FindWindow and BringWindowToTop but none of them seem to work.
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Jan 10, 2012
I am following some instructions that apparently work with vb6, but as i have downloaded the lastest version of visual studio i think its up to version 10.
The code i am trying to make work is,[code..]
I searched a bit for an equivalent.
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Jan 10, 2012
I am following some instructions that apparently work with vb6, but as i have downloaded the lastest version of visual studio i think its up to version 10.[code]The error is that hWnd is not a member of windowsapplication1.form1.
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Oct 17, 2011
I'm using a third party dll for my project and one of the function that is provided by the dll use form handle as one of the argument. But when i call the function, I'm not using any window form and it's just called from another class. So what value i should put for that argument?Here's the example of that function:
AVS_Measure (device_handle, form_handle, no_measurement)
After this function has been called, it will send message to the form_handle argument whether the measurement data is available and valid.I called this function from another class just for triggering start measurement and i have another function to retrieve the data. I do not have any form associate to it, what value i should put for this argument?
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Apr 5, 2012
I'm writing a DLL library that interfaces to a USB device using winusb in VB.NET.
Since it's a DLL, I have no window, and it's possible that users of my library will also not have a window (command line apps, for instance).
The examples I've seen that detect device attach and detach all use RegisterDeviceNotification which requires a window handle to receive the attach/detach messages at.
How do I receive these messages directly into a function without a window to get a handle from?
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