C# - Blocking A Thread In .Net?
Aug 13, 2010
I have a class that has purely static Methods and properties. I am calling an async method on the class "Load" that asks a web service for a chunk of data, which then fires an event that executes the return method, "LoadCompleted". I have no idea how long the call is going to take (the difference between calling the "Load" method, then the "LoadCompleted" getting called).
I would like to block the application from proceeding any further until the callback method has been raised (as the app will try and get stuff from this class, which isn't populated until the "LoadComplete" method sets the data).
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May 24, 2011
Is there a synchronous wait function that won't tie up the UI-thread in .NET WPF? Something like:
Sub OnClick(sender As Object, e As MouseEventArgs) Handles button1.Click
Wait(2000)
'Ui still processes other events here
MessageBox.Show("Is has been 2 seconds since you clicked the button!")
End Sub
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Jan 19, 2009
I have been reading the async design patterns on MSDN and the general idea makes sense to me but in practice it is proving to be more difficult. I am working on a project utilizing VMWARE VIX.
HTML Code: [url]. Each function such as connecting to a host server, retrieving properties, etc. can be executed in two different ways.
Connecting to a host using a blocking Wait:
Code:
Dim m_lib As New VixLib
Dim m_hostJob As VixCOM.IJob
[CODE]...
Code:
Dim m_lib As New VixLib
Dim m_hostJob As VixCOM.IJob
dim m_callback as VixCOM.ICallback
[CODE]...
The problem with the VIX SDK is that sometimes the functions never return, hanging the application. dblock.
HTML Code:[URL] came up with a library that specifies a timeout value. When the timeout runs out the method aborts and returns regardless whether it finished or not.
The callback method is an active wait where the code continues to execute. What I want to implement is a blocking wait with a timeout. The ICallback interface has one sub OnVixEvent(IJob,Integer,IVixHandle). This method is fired at least twice, first when some progress is posted and second when it is complete. The first call to this method can be one second after registering the callback or 30 seconds, so I can not rely on this method to block the main thread. how to create some kind of async result class that would block the main thread from executing until either a timer runs out or the OnVixEvent method returns an Operation Complete signal that also implements ICallback.
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Jun 29, 2011
I am a novice in Threads, but I want to know how to order thread execution in my scenario, and is the following :
UI Thread : Windows Form Background
Thread : Kind of print daemon
implemented with recursive methods
IO Operation : a StreamWriter that do
the job of File.AppendText()
When I execute my main app.exe, sometimes it launches the Windows Forms and the execution process in the task manager (app.exe), in some opportunities its just launches the execution process in background. How can I determine the behavior of launching UI, I have to establish a priority or somewhat else? Code: I'm using framework 2.0 and any answers could be writted in C# or Vb.Net.
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Nov 18, 2011
I'm in the Progress of changing a big Application from Singlethread logic to Multithread logic. I'm currently move Dataloading Logic into a sperate thread, and work with callbacks after they are finished. I have Synclocks in place in order to ensure threadsafty. But sonetimes the Synclocks wait even if there is no other thread with the same synclock active. Is there any way to find out what witch thread they are waiting for, and why? BTW, I have FW45 installed, may that be the reason, since it'S a inplace upgrade for FW40?
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May 6, 2009
In my DoWork() function I register with our sip server. Then I have to wait for a response back. However, the response I get is received in another event. However, before I am able to check the flag in the DoWork() the DoWork() has all ready finished and the response comes after.
I am trying to find a way to wait in the DoWork() until I get a response in the Diagnotic event. I have a global flag that is set in that event that I have to check in the DoWork().I was thinking of maybe blocking in the DoWork() until the other event is finished. Maybe using a join.
' Do work in background worker
'Will return less than 8 if there are no error message from the library
If (Not Me.bgwProcessLogin.CancellationPending) Then
' Register and wait for response
[code]....
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Jan 15, 2012
I've been reading up on asynchronous function / web pages for ASP.NET 3.5 (we're not using v4 yet) but the ones I've seen all focus on performing a background task but then still coming back to finish up and send the response, after the task is complete.
What I want to do is simply kick off the background task (in this case a call to a web service) but then return a response to the browser immediately - ie. without waiting for the asynchronous task to complete. I don't even need to know if it succeeds or not.What is the best way to do that? I can't seem to find examples of kicking off what you might call an "orphan" background task in ASP.NET.
I thought of doing it via a javascript Ajax call on the page I show to the user, but the information passed to the web service is sensitive, so that's out of the question. But that kind of illustrates what I want to do.
[ed] Another idea: Is there an event in the ASP.NET model I can use which occurs after the response has been sent to the browser and the connection closed? ie. So more processing can occur without the user waiting for it?
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Jul 17, 2009
when a button is clicked i start a seperate thead which is population a grid and does something with a webbrowser-control. But when the button is click the new thread seems not to be seperate, cause the UI is freezing until the new thread is done.
[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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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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May 4, 2010
I was wondering if it would be possible to block a website, such as "www.proxy.com"
Through Internet Explorer, not one of my custom ones of my form.
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May 25, 2012
The subject sucks, but the problem is straightforward. I have an existing WCF service. There are a small series of functions, currently. One or two of the functions will need to be performed with a bit of security, for which I need a username and password. The username and password will be checked on the server side against a webservice running on localhost. One alternative is to not use the localhost webservice for the validation, but then I wouldn't have a question, so ignore that.
The way the webservice will work, I was thinking that I would use an invisible web browser, navigate to the REST-style URL, and wait for the response. It's the bit about waiting for the response that is causing me trouble. Normally, I'd wait for the document comleted event raised by the browser control, but since this is initiated by the call of a WCF service function, that won't really work. The WCF function call can't 'wait' for anything, nor will it receive the event. Once the WCF function reaches the End Function statement, it is over and done with, and returns. The response from the webservice won't have arrived by then, so that won't work. There are two typical solutions to this, one of which is horrible to the point of being unworkable.
1) A busy wait, or spin wait, where the WCF function goes into a tight loop waiting for the browser event to be raised. This is never a good idea, and is particularly terrible in this case, because the WCF service is running on a web server, so the negative impacts of a busy wait are FAR worse than normal.
2) Use something like a Mutex in the WCF function such that the function launches a thread, the thread immediately grabs the Mutex, then begins the navigation. The WCF function waits on the Mutex, which would mean blocking without spinning, and the document completed event pulses the Mutex to release the WCF function so that it can return the proper response. This seems technically improbable, as it stands.
The problem is only a slight variation on a very typical problem, yet it presents some interesting problems. Windows is event driven, but a WCF service function is not. A callback across a WCF (at least across this one), isn't an option, events aren't an option, so it all comes down to the function starting a process, then blocking without spinning, until the process comes up with an answer.
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Sep 20, 2009
I am trying to make an app in VB.NET that pings ip's on a specfic port that are connected to my computer and if it is greater then 500 the person would be blocked from connecting to my computer. How can I do this in VB.NET?
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Oct 10, 2009
I am creating a security program. One of its features is that it blocks inappropriate web sites. I might need help determining which sites are bad and which ones are good. If I could 'read' every work that is displayed in the browser then I could tell, but that may come later.
So, I'm looking for some kind of hook that will allow me to cancel the site if needed. It should be able to still be hooked in Safe Mode, as well... I'm sure that this is going to be an easy one!
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Sep 9, 2010
I wish to block websites in a browser, where the blocked websites are stored in my.settings.blockedwebs (which is a collections. specialized. stringcollection). I let the user input the blocked website into a textbox in form1, and the add website to the stringcollection button has the following code:[code]
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Jul 27, 2009
I am unable to get on to internet explorer or IM on my laptop . I am using Windows XP.Each time I log-in it says my firewall is blocking.
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Apr 30, 2012
I'm trying to wait for a Task result in .NET 4, much like you can by using the await keyword in .NET 4.5. I just can't figure out how to do it though...My code (to prove that I'm atleast trying):
Private Function GetXDocumentFromWebLocationAsync(ByVal request As WebRequest) As XDocument
Dim queryTask As Task(Of WebResponse)
queryTask = task(Of WebResponse).Factory.FromAsync(AddressOf request.BeginGetResponse, AddressOf request.EndGetResponse, Nothing, Nothing)
[code]....
As you would expect, the GetResponse calls are executed on a different thread, but the function has to wait for the result before it can return. Unfortunately this blocks my main thread until the task has completed and I don't have the slightest clue on how to make it wait without blocking. I don't want to use the Async CTP either because that's just running away from the problem.
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Aug 27, 2010
Is there a way to include an ActiveX to VB .NET project without adding it to a form?
If I add it to the form and call a function on it that blocks, the UI is unresponsive until the function returns. Even if I am making the call in a different thread.
I was able to compile the code when I did not include it via the form, but got this error once I called a function on it.
Catastrophic failure (Exception from HRESULT: 0x8000FFFF (E_UNEXPECTED))
How could I make the UI responsive when the ActiveX functions are blocking?
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Jul 31, 2011
I create a .net dll on the fly with codedom then I load it with Assembly.LoadFrom like this:
Private Sub Test()
Dim ASM As Assembly = Assembly.LoadFrom("test.dll")
'Do some stuff with the loaded assembly...
[code]....
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Apr 11, 2012
I am trying to block a list of processes from Txt file/ Listbox System.Diagnostic.Process using Timer. Here's the timer codes
[Code]...
I can block processes from the list using SelectedItem, but it doesn't block all the process in the list.Using while loop causes a deadlock error here. I'm now using aBlock.ReadLine to read from txt file and block the available process. However it is only able to block the first process. Need some guidance to get this code to block all the processes in the list.
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