Winforms - .NET 2.0 - StackOverflowException When Using Thread Safe Calls To Windows Forms Controls
Sep 22, 2011
I have a Windows Forms app that, unfortunately, must make calls to controls from a second thread. I've been using the thread-safe pattern described on the [URL].. Which has worked great in the past.
The specific problem I am having now: I have a WebBrowser control and I'm attempting to invoke the WebBrowser.Navigate() method using this Thread-Safe pattern and as a result I am getting StackOverflow exceptions. Here is the Thread-Safe Navigate method I've written.
[Code]...
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Jun 2, 2012
I am trying to access a dynamically generated Control from a separate thread. But I am always getting a "Stack Overflow Exception" with my code. I am using following code:
[Code]...
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Sep 20, 2011
[URL]
In my program, I created a list of a class that contains 5 picture boxes, a button, a label, an identifier, and some other stuff. I've got roughly 65 of these in this list. I'd be stupid to hard code all that in. The identifier is a 2nd way of identifying which specific location I'm working on.
Anways, all this is created at compile time. Works perfectly fine.
I then manually start a background worker that pings a collection of components. Based off the success of those pings, the picture boxes are enabled or disabled. Basically a proactive way to see if a collection of devices over multiple locations are actually working.
It's the background worker that fails because of thread-safe calls.
Private Sub bgwStatus_DoWork(ByVal sender As Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles bgwStatus.DoWork
Dim status As Integer
[Code].....
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Sep 5, 2011
I need to implement, Controls Based Security in a Windows Forms Application using VB.NET. I tried google but did not get anything much to work with.
I would like if someone, could suggest some books or tutorials.
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Sep 8, 2010
I have pairs of controls: immagebox + textbox = one pair.I want these to show up in a single column grid/tabular format.Each cell contains one image/text pair.I want this grid to scroll because the number of pairs is dynamic depending on a user selection.I suppose I will be adding these controls in code at runtime when the user makes his/her selection.
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Mar 25, 2012
''//begin cross threaded component
Private Sub dBgRIDvIEWNotInvokeRequired(ByVal dBGridViewcomponentname As DataGridView, ByVal dvalue As String)
dBGridViewcomponentname.Text = dvalue
dBGridViewcomponentname.Update()
[code]....
when used is like this CrossThreadedDbGridView(DataGridView1, "TheText") But what if I have lots of member or property to used like this code:
DbGridPapers.ColumnCount = 5
DbGridPapers.RowCount = rc
DbGridPapers.Update()
[code]....
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Apr 14, 2011
An unhandled exception of type 'System.StackOverflowException' occurred in System.Windows.Forms.dll it also says make sure you do not have infinate loop or infinate recursion il give all code in order that they are executed in Check the chechbox and it disables all irelevent stuff and populates the combobox
Private Sub CheckBox_Spray_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CheckBox_Spray.CheckedChanged
If Me.CheckBox_Spray.Checked = True Then
[code]....
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Mar 13, 2012
Imports System.Threading.Thread
Imports System
Public Class Form1
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Me.demoThread = New Thread(New ThreadStart(AddressOf Me.ThreadProcSafe))
[code]....
I've been trying to use Microsofts example on their MSDN but I'm getting this error. :
Error1'demoThread' is not a member of 'WindowsApplication1.Form1'.C:UsersAydinAppDataLocalTemporary ProjectsWindowsApplication1Form1.vb89WindowsApplication1
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May 9, 2012
If you are interested, I am doing this because I do not like having to drag and drop my browser etc. I just right click the URL in Chrome and select (Play on My TV) a customized dropdown item, at which point my Player finds the TV, opens the URL, maximizes itself and plays the content
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Apr 21, 2010
I'm getting the following error:"Current thread must be set to single thread apartment sta mode before ole calls can be made"
I am using Speech.Recognition.SpeechRecognizer and using it to open various dialog boxes. It works fine for the first few but on the third one when it calls the InitializeComponent in the Dialog's New, it throws the above error.
Anybody have any clue what causes this or how to fix it? The SpeechRecognizer seems to run on its own thread, so that seems to be at the root of the problem. If I open thedialog with a button click I don't get an error.
[Code]...
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Jul 26, 2010
I have a thread in an application which calls a sub routine Main(). The Main sub routine in turn call several sub routines/functions from with the same module,several different classes in the same application. Also some sub routines/functions call routines from a class library. Now say the routine/function in class library goes into a infinite loop and never returns. I would like my thread in the application to raise a event and display message to the users about the infinite loop. I am giving some sample code for the application.
Imports System.Threading
Module VMain
Public gbSuspend As Boolean
[CODE]...
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Feb 19, 2010
When I run my project I get "An unhandled exception of type 'System.StackOverflowException' occurred in System.Windows.Forms.dll"
Public Class frmViewReport
Dim objForm As New frmViewReport
Private Sub frmViewReport_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
objForm.ViewReport("C:a2.rtp", , "@parameter1=test�mter2=10")
[code]....
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Jul 24, 2011
I've successfully saved video files into SQL server as varbinary. Now, my problem is, how can I play those videos in Windows Media Player (embedded in my Windows Forms).
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Nov 11, 2009
I'm writing a little online game for sport, but my head's gonna explode as I can't figure out why I can't access my forms controls from my clients DoRead() thread.In this procedure I can still obviously access the controls normally.[code]Tried using delegates and invoking, and setting SearchForIllegalCrossThreads false.
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Oct 18, 2011
I am retrofitting unit testing into a fairly complex system designed and written by other developers in VB.net. I am trying to develop unit tests for the GUI forms using NUnit and the NUnit Forms extension. (I've been looking at c# examples that are fairly easy to port over if you have a solution but don't know VB syntax as long as it uses NUnit classes)
I will try and explain what I am doing but first a brief description of the program. It basically monitors server activity. You need to connect to a server via a modal form with IP and Port fields(amongst others). Once you have connected to a server other parts of the program unlock and become usable (such as configuration of the server).
Desired process: Load program > click connect button > modal connect form loads > enter details > click OK to connect > main form updates to logged-in state > other functionality
The problem is that I cannot test the functionality of the connect form and then the logged-in functionality of the program. I can test that it loads the modal connect form correctly; enters the details and clicks OK (all fine so-far) but it does not appear to logically progress the program. The modal form just closes again seemingly without running the connect code from the program back-end and I'm back at the main menu not logged in to anything.
I have a feeling that I've either missed something really obvious or that it's simply not doable in NUnit.I have trawled the internet in search of anything similar but the closest was another SO thread that was really generic. Without being able to actually test the logged-in version of the program, I'm at a major hurdle.Another issue is handling message boxes that don't have unique identifiers (e.g. "are you sure you want to exit?"); these also seem to be a major pain in the arse with NUnit (If it makes any difference, I'm running the tests as a stand-alone project using a reference to the executable file of the built project, not the actual source)
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Jun 10, 2012
I am retrofitting unit testing into a fairly complex system designed and written by other developers in VB.net. I am trying to develop unit tests for the GUI forms using NUnit and the NUnit Forms extension. (I've been looking at c# examples that are fairly easy to port over if you have a solution but don't know VB syntax as long as it uses NUnit classes)I will try and explain what I am doing but first a brief description of the program. It basically monitors server activity. You need to connect to a server via a modal form with IP and Port fields(amongst others). Once you have connected to a server other parts of the program unlock and become usable (such as configuration of the server).Desired process: Load program > click connect button > modal connect form loads > enter details > click OK to connect > main form updates to logged-in state > other functionality
The problem is that I cannot test the functionality of the connect form and then the logged-in functionality of the program. I can test that it loads the modal connect form correctly; enters the details and clicks OK (all fine so-far) but it does not appear to logically progress the program. The modal form just closes again seemingly without running the connect code from the program back-end and I'm back at the main menu not logged in to anything. I have a feeling that I've either missed something really obvious or that it's simply not doable in NUnit. I have trawled the internet in search of anything similar but the closest was another SO thread that was really generic. Without being able to actually test the logged-in version of the program, I'm at a major hurdle.Another issue is handling message boxes that don't have unique identifiers (e.g. "are you sure you want to exit?"); these also seem to be a major pain in the arse with NUnit(If it makes any difference, I'm running the tests as a stand-alone project using a reference to the executable file of the built project, not the actual source)
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Mar 5, 2009
I'm using the following code to validate the text entered by user. It works perfectly fine. But I want to add the backspace feature so as to allow the user to delete the wrongly entered number.I have tried a couple of things and they worked but before last digit (after the decimal point) i.e. it does not allows to delete after the number has been completely entered.number is being entered in the format: 12313213.45
What shall I do?Private Sub TextBox5_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox5.KeyPress
[Code]...
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Apr 25, 2009
how to do word wrap in drawstring in vb.net 2005.
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Apr 19, 2012
I'm calling a c++ dll I made myself - and it appears to be very VERY not thread safe!
I'm referencing it like this
<System.Runtime.InteropServices.DllImport("D:ACS DesktopdcxdcxDebugStringLibrary.dll", EntryPoint:="firstIndexOfKeyword", CallingConvention:=Runtime.InteropServices.CallingConvention.Cdecl)> _
Public Shared Function firstIndexOfKeyword(ByVal s As String, ByVal substr As String(), ByVal substrLength As Integer, ByVal markers As Integer()) As Integer End Function
Is there a way to make this IMPORT create something more threadsafe?
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Feb 27, 2012
I'm dropping into this function - from several threads - to add an OBJECT to a dictionary collection
Private Delegate Function ReaderRegisterDelegate(ByRef rrFSOb As FSObject) As FSObject
Private Function ReaderRegister(ByRef rrFSOb As FSObject) As FSObject
Try[code].....
It's getting Object reference not set to an instance of an object.The FILEID key being added is F1. F2, F3 and F4 are in the dictionary. Seems like F1 arrived and the object wasn't properly setup. Or thread-slice caused me to see a partially messed with dictionary list?How can I make that a thread safe operation? I thought dropping out to the UI thread was a safe place to mess with code like this? Oddly enough I can go to the immediate window and do this
m_FSObCollection.Add("F" + rrFSOb.FileId.ToString, rrFSOb)
?m_FSObCollection.Count 4
ex.data is a dictionary list that looks like this
directcast(ex.Data , System.Collections.IDictionary).Count 0
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Jun 25, 2009
In C# Windows Forms, a user control's InitializeComponent is called from the form's/control's constructor. When I create same scenario in VB.NET I don't get a constructor, and I can't locate a place where InitializeComponent is called.I need to call my code between InitializeComponent and when the control's Load event is raised, preferably still in the control's constructor. How do I do this in VB.NET?
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Nov 2, 2009
Let's say that I have a module that has a Queue in it. For other entities to Enqueue, they must go through a function:
[Code]....
If I have multiple threads running and they want to call InsertIntoQueue(), is this considered thread safe? I am under the impression that there is only one copy of the instructions in memory necessary to perform the InsertIntoQueue() function... which would lead me to think that this is thread safe. However, I wonder what happens when two threads attempt to run the function at the same time? Is this thread safe, and if not, how can I make it thread safe? (and What would be the performance implications regarding speed and memory usage)
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Jul 26, 2011
I have a TCP server app that starts 2 threads when the server is activated, I want the threads to add text to the textbox on the main form. Here's is what I have tried [code]I have added MsgBoxes at points so I know the Sub updatetext_ is being called, and the text is being passed, they are also showing that InvokeRequired is always FALSE. In any case the textbox txtMessages is not being updated.
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Sep 5, 2009
On the MSDN docs for the generic List(Of T) class, it says this:
Quote:
Public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.but I'm trying to work out what exactly that means or why it matters. Does that mean that if I had this:
vb.net
Public Shared MyList As New List(Of MyClass)
then I could enumerate through that list from several threads at once without there being a problem? I thought you could read from any object from multiple threads without a problem anyway... I thought it was only if there were potentially other threads modifying that object at the same time that there were problems. Particularly with a collection like a List because you cant modify a list while another thread is enumerating the items in the list as you get an exception thrown stating that the collection has changed. I think basically what I am asking is if the MSDN doc said that a public shared list wasnt thread safe then what difference would it make?
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Feb 21, 2011
I am trying to add a subitem to a listview in a threadsafe manner.In a single threaded application it works like so:
[Code]...
However if run in another thread it causes a cross threading error.I have looked at examples of delegate subs that use Invoke, but all examples i have seen involve updating the text property of an object, and i cant get my head round how to apply the concept to actually add a subitem to a listview.
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Jun 19, 2011
I'm receiving tons of statistics data that I need to insert into the db.I would like to implement some kind of Queue or FIFO class that keeps all the dataand when it reaches to a specific count (buffer), it will send that data to the SQL through bulk insert. This should be thread-safe.
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Jun 22, 2010
i got a background worker that has the following code in the do work.... one of the things i want to do is to add rows if theres none available ...but i got an error saying i need to do a safe call thread...i already read about it but im stuck i put control.invoke, but that gives me an error too saying Error 1 Reference to a non-shared member requires an object reference.
[Code]...
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Mar 1, 2011
Im creating a service for a mobile platform and I need to process user messages on a different thread than they were created on to leave the threadpool open.Anyway my App will be using a MySQL database and when it gets a message it will add the message to Another thread pool. But in the sub that procceses the messages I will need to perform query's on the database. So i know i can use a global variable and it will be visible to all threads but is making database operations safe while using a thread pool with a global mysqlconnection?
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Sep 16, 2009
I currently have a form with a listview. On another form, I would like get all the items from that listview. This I can achieve but I always get the "Cross-Thread operation not allowed exception" message. I've tried the following code to avail.
[Code]...
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Aug 26, 2009
I am using WCF to make a chat application - I dont think the fact I'm using WCF is relevant for this particular question but just thought I would mention it in case there is something special about the way WCF does threading that I dont know about.So I have my WCF service that runs on a server and a WPF app that acts as the WCF client - each time a new client signs in or out it updates the server WCF service to let it know that it has changed status. The server then updates a list to either add or remove the user, so this list basically represents who is online at any one time. The list is declared in the core server class like so:
vb.net
Private Shared List(Of ChatUser)
So, I have a method in my server side that is called whenever a user needs to be added to this list and originally I thought I could have some issues because while the server might be looping through this list to find out who is online, another user might have signed out and the list would therefore be modified while the server was looping through it which would cause an exception. So I added the following to the start of the method that removes a user from the list:
vb.net
SyncLock New Object
and I havent had any problems... but I'm still not totally convinced that this will completely solve the issue. So would creating a Property give me a bit of extra safety? Assuming I always used the property to access the list in my code.
Like this:
vb.net
Private Shared Property CurrentClientList() As List(Of ChatUser)
Get
SyncLock New Object
[code].....
Also, am I actually using SyncLock correctly? I mean should I be referring to a shared object that all of the threads can access rather than just doing New Object each time or does it not make a difference?
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