BackgroundWorker.CancelASync() NOT Canceling Bg Worker?
May 13, 2010
I've set up a background worker to search a directory for emails and if my specifi criteria (i.e. date ranges, contains a word) are fulfilled, then a list view is populated.I have this working absolutely fine - when I click search, the list view is populated as I watch - but when I press my 'Stop' button, which runs bg.CancelASync() it does not stop the process at all - results still populate in the list view as it was before.
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Apr 30, 2010
I have been looping thru the backgroundworker, after running a few hours, i found out that it stop even though i did not call cancelasync(). Below is the code:
Private
Sub
SboT_BgWorker_DoWork(ByVal
[Code]....
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Nov 18, 2009
Ive read through tons of forums, but my Backgroundworker1.CancelAsync still isn't working.I have Form1 that shows Form3(see code).when btn_submit is clicked on Form3 it runs the backgroundworker, copies a file from one place to another, and shows the progress in the progressbar.Form3 contains: lbl_message, btn_submit, btn_cancel, ProgressBar1, BackgroundWorker1 (with Workersupportcancelation = true.)When i click on the btn_cancel the copy continues, so i assume the backgroundworker has not stopped.[code]
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Feb 22, 2009
I'm trying to create an app with a backgroundworker to enable canceling a loop, but it won't work as I hoped it would.When I debug right after the line ThreadWorker.RunWorkerAsync() the programm goes directly to Private Sub ThreadWorker_RunWorkerCompleted and skips the Private Sub ThreadWorker_DoWork part, where of course the actual code is in (I've left that code out, it's about a 100 lines and without BGW it works).Does anyone have an idea what could be wrong with it?
[Code]...
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Jun 16, 2011
I have a VB.net project which uses a background worker to do some stuff.
Now I want to expand the project to be able to do multiple stuff :)
A user can enter an URL in a textbox and when the user click on the parse button the program creates a new tabcontrol a outputs some data.
I use a hardcoded background worker for this.
But now I want to run multiple background workers to do this stuff so I can't rely on hard coding the background worker(s).
Is it possible to create background workers dynamically.
how to set this up since I think I need to set up the different methods and variables like:
Private bw As BackgroundWorker = New BackgroundWorker
bw.WorkerReportsProgress = True
bw.WorkerSupportsCancellation = True
[Code]....
I think I need to declare the background workers in some sort of array like variable (list / dictionary)??? Other then that I have no idea how to tackle this.
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Nov 30, 2009
I found like 100 tutorials for this background worker, but none for my needs I want to cancel the thread using CancelAsync() , but all the tutorials do it only in a loop, like this:
Private Sub BW_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BW.DoWork
For i As Integer = 0 To 30000
If BW.CancellationPending Then
e.Cancel = True
[Code]...
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Mar 11, 2009
I have the following code that adds a background worker into a VB.net WPF project:
Imports System
Imports System.ComponentModel
Imports System.ComponentModel.BackgroundWorker
[Code].....
And I get the following error for the DoWork worker event:
Handles clause requires a WithEvents variable defined in the containing type or one of its base types.
It seems like it's missing something in the Event declaration, but can't find it.
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Dec 14, 2009
in my button click event i ececure
If BackgroundWorker4.IsBusy Then
BackgroundWorker1.CancelAsync()
End If[code]....
after proceess completed if press the button again.i got the following error msg
This BackgroundWorker is currently busy and cannot run multiple tasks concurrently.
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Aug 17, 2009
I'm using a While loop that loops a certain number of cycles (1-576) based on a value entered by a user. It's activated by the user clicking a "Start" button, But I would like it to be able to be canceled using, preferably, the "Escape" key. However, when the loop is going I can't get the program to recognize any keypresses.
[Code]...
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Dec 10, 2009
I have a program in VB2008 and I need to execute a thread from differents Subs.Each time I start the thread I want to cancel the previous.Here an example:
Private Sub TextBox_Changed(ByVal sender As System.Object, ByVal e As System.EventArgs) Dim ThreadResults As New Thread(AddressOf ShowResults) ThreadResults.Start() End Sub Private Sub ckBoxAllRecords_CheckedChanged(ByVal sender As Object, ByVal e As System.EventArgs) Dim ThreadResults As New Thread(AddressOf ShowResults) ThreadResults.Start() End Sub
I write in a textbox, TextBox_Changed fires, thread spend 4 minutes filling a dataset I check a checkbox, ckBoxAllRecords_CheckedChanged fires, thread spend 10 seconds filling a dataset.I dont want anymore the dataset of TextBox_Changed so I want to cancel its filling.
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Mar 4, 2010
I have a DataGridView in which I register customer orders.
The DGV has a column "PRICE", Price must be > than 100, and I control that in this way:
Private Sub DataGridView1_CellValidating(ByVal sender As System.Object, ByVal e As System.Windows.Forms.DataGridViewCellValidatingEventArgs) Handles DataGridView1.CellValidating
Dim newInteger As Integer
[Code].....
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Nov 21, 2010
I'd like to start by saying that simply though searching, DreamInCode has taught me alot about VB.NET. In fact, I would imagine without DIC as a resource, I probably wouldn't have been able to move forward and learn most of what I know now, just because I got stuck on some things here and there.Anyway, I searched around for information regarding how to "capture" a minimize event in VB.NET. I am working on the GUI for an application that I would like to have minimize to the system tray. Currently, instead of accomplishing this with the minimize function, I do it on the FormClosing event like this:
Private Sub MainFrm_FormClosing(ByVal sender As System.Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles MyBase.FormClosing
'Cancel the attempt.
[code]....
That code works, and upon making the form visible again with Me.Visible = True the form is restored to its original position. However, prior to the form being hidden, the window manager draws a minimize and restore effect before eventually hiding it. Any change to the WindowState _after_ hiding the form does not appear to have any effect, so when the form is unhidden it is still minimized.is there a way to capture Minimize events, and when captured, is it possible to cancel them in a manner similar to what I did with the FormClosing event?
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Sep 17, 2010
Really wracking my brain here and I'm sure it's something simple I'm missing. Basically I have a form with two tabs. I'm checking the controls on each tab to see if they're dirty and want to prevent a user from clicking a tab if there are changes on the current tab.
I had thought if I check the dirty variable and just set the tab index to the one that hasn't been selected I'd be fine but every time I programatically set a tab's property, it fires off a bunch of the tab's events that just produce an undesireable result such as the right control set is showing but the wrong tab is selected. Here is the code for as close as I've gotten to getting it to work.
[Code]...
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Aug 14, 2009
I have a task that needs to be executed many times in a thread, so as to keep my GUI responsive. Right now I'm using the ThreadPool to accomplish the tasks, and it works perfectly. I get all the data I expect back from the threads, life's good. When those tasks are finished, I then fire off another set of threads to accomplish another set of tasks, in the same fashion. The work method of these threads uses a call to RegistryKey.OpenRemoteBaseKey, which does exactly that, opens a remote registry key. The problem is: if the user running the application does not have permission to open the remote registry the call will throw an IOException, but I expect this behaviour because the user does not have permission to do it. However, the call itself can take FOREVER.
I wrote the application initially to use delegate methods and used the WaitHandle.WaitOne() method on AutoResetEvents in a state object I passed to each delegate. I tried the WaitOne method using a timeout, which worked fine until I realized that even though the WaitOne timed out, the thread was still running. This is a problem because (from what I understand) processes are only given a certain number of ThreadPool threads and, once used, they must be finished in order to be released back to the threadpool. In my work method, I also have a variable that can be signalled when the thread should be stopped, but that (obviously) only works on code that I've written.how can I cancel a thread that's stuck on a .NET method? Is there some sort of garbage collection method I can call if I give it a handle?
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Jul 18, 2010
Right basically if a checkbox in my application is checked "Close to system tray" then my form will cancel close and send to tray instead
[Code]...
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Oct 12, 2009
Protected Overrides Function ProcessDialogKey(ByVal keyData As Keys) As Boolean If keyData = Keys.Enter Thenme.currentcell.value = "Hello" ' Here i want to give text "hello" to the current cell is this possible
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Apr 2, 2012
i'm in the need to start a backgroundworker inside another one.Now...The first one BGW starts a for cycle, and inside this one there is the second BGW that has to upload an image to a server.The trouble is that, the progress event and the complete event of the internal BGW are never called.
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Jul 15, 2011
I'm writing an application in Visual Basic Express 2008, part of the function being to walk through a folder structure starting from a user specified folder. In my research, I found this thing called a background worker which seemed an appropriate tool to use given the potential size of a target folder structure. I successfully installed the two examples from the library here, and believe I understand the principles involved. Even so, having tried to build this feature into my application, it seems as though it is not working as expected, and, as predicted, debugging a multi-threaded application is a pain in the extremity.
I have this fragment under my "start" button click event -
HomeSource.Enabled = False
HomeCopy.Enabled = False
HomeReport.Enabled = False
[Code].....
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Jul 18, 2010
im thinking just because an app has been sent ton system tray does not mean its a "back ground worker"
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Jun 7, 2012
my backgroundworker as I just cant get it to work. Basically I have a backgroundworker which does a few tasks but I'm trying to implement a progress bar and a label. I'm going to set the maximum value of the progress bar to 10 and then have it updating as I move with each task, also I'm thinking of a label with the progress bar which will display the progress ie
[Code]...
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Oct 7, 2009
I'am trying to make app that will show every file in C:[code]Now how can i add progress bar with the background worker.
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Nov 20, 2008
I have a background worker that used to fire its RunworkerCompleted event when its DoWork routine finished querying a database and writing its output to a file. The bg worker was in a class called Query, which was called from another class called Trigger. A new Trigger Class was created for each monitored event. In this class, there was a structure which stored the config of each Trigger. When this event was triggered (set to TRUE) a new query class is created and it is passed the Trigger class. When the database query, file writing was done, the query class and all its rsources were diposed from the RunWorkerCompleted EventRecently I changed the application so that a new trigger class is not created for each monitored event. There is a single instance of the class but new config structure for each event. When a particular event is trigger, jsut the config structure is passed to a new query class and the sma ething is done in the query class. I just noticed now that the RunWorkerCompleted event is not being fired anymore.
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Apr 15, 2009
I have an issue that I can't seem to find a straight answer for anywhere... I have a For loop that sends a file name to a background worker that contains some long running code and I can't find a way for the parent thread to wait for the background worker to finish... Here is the example code:
For 4
BacgroundWorker1.RunWorkerAsync(fileName(i))
Next
[code].....
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Sep 21, 2009
I have run into this before, When I develop a form to use a background worker to fill tableadapters, the background worker does fine on machines running Vista, but if you run the same thread on an XP machine, the thread gets hung.All the thread is doing is filling a table adapter like this.[code]Why would this run on a Vista machine and not an XP machine?
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Apr 27, 2010
I have created a background worker to go and run a pretty long task that includes creating more threads which will read from a file of urls and crawl each. I tried following it through debugging and found that the background process ends prematurely for no apparent reason.
While Not myreader.EndOfData
Try
currentRow = myreader.ReadFields()
Dim currentField As String
[code]....
This first bit of code is the loop to input from file and this is what the background worker does. The next bit of code is where the background worker creates threads to work all the 'landingPages'. After about 10 threads are created the background worker exits this sub and skips the file input loop and exits the program.
Try
For Each landingPage As String In landingPages
pgbar.Timer1.Stop()
If VisitedPages.Contains(landingPage) Then
[code]....
Also my main thread runs a forms from where this background is called to run but the main thread is supposed to wait for the background process to end unless the user selects another option from the main form.
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Jan 11, 2012
I've been experimenting with background worker to maintain responsiveness and to allow the UI to update while things are being done in the background.I've been having problems getting the background worker to do anything with form controls.For simplicity lets say I have form1 and form2.The background worker is on form1Initially I couldnt get it to edit controls on form1 but by using [code]However the problem came when I tried to get the same background worker to update controls on form2, in this case a text box. With the above code there is no error but it also does not update the text box.Is there an easy way to give a background worker access to multiple forms.
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Dec 27, 2009
I have some class that splits some work onto multiple worker threads. To be more specific: the class represents a download, that can have as many segments as the user wants, that get then put onto separate threads.When I run the download with one segment, it works fine. When I run it with 2 segments, the second segment encounters an error.[code]When I put a breakpoint on the if, it'll stop there, but when I go to the next line, I get an error.I don't get what's getting wrong, and got a headache after a few hours of attempting to keep track of the correct thread.Anyone an idea what's going wrong, or how I can detect it better? (This is the first time I'm doing real multi threading debugging.
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Mar 10, 2011
i m trying to kill a background worker in the do work event of the worker i was using
backgroundworker.CancleAsync()
but its shows an error saying tat CancellationPending does not allow
how can i kill a background worker after its work gets completed in its do work event
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Dec 30, 2011
currently, i have this code: My_BgWorkerB is the Name of my BackGround Worker
If My_BgWorkerB.IsBusy Then
If My_BgWorkerB.WorkerSupportsCancellation Then
My_BgWorkerB.CancelAsync()
[code].....
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Apr 16, 2009
Is there a way to pause a background worker? What I need to do is pause a background worker when it encounters a file error, wait for a few seconds, and then carry on.
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