Possible To Update UI From BackgroundWorker DoWork Event?
Sep 22, 2010
I have seen others with a similar issue but not quite what I was looking for. In the backgrounderworker class dowork event I create an instance of a new class and call one of it's function. Previously, I had this code in a windows.form.timer tick event and would pass a delegate in as one of the parameters which would allow the function and other functions it calls within the class to call a method on the form to update a datagrid on the GUI. Is there a way to do this within the dowork event? I need this because the function I call from dowork calls other functions and I want each of those functions to log information in the GUI datagrid.
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Oct 6, 2010
Let's say a custom exception is thrown in the DoWork event for a backgroundworker. How do I pass the custom exception to the backgroundworker so that it ends up being the e.Error in the RunWorkedCompletedEventArgs?
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Mar 26, 2010
How would you create and use a delegate to update the text of the main form from the DoWork event of a backgoundWorker?
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Aug 30, 2009
As I teach myself VB, I'm working on using the backgroundworker. Mostly I'd like to use it to update a progress bar. But here the problem I'm running into...
When I use it like this:
Private Sub TestWorker_DoWork(ByVal sender As Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles TestWorker.DoWork
Dim ListText As String
For Value As Integer = 0 To 100
If TestWorker.CancellationPending Then
[Code] .....
Where GetPlayerNames() is the Sub that really contains a majority of my code, which uses a class library I wrote, and calls other functions, etc. But this just causes the backgroundworker to skip right to the RunWorkerCompleted and executes no code. It seems to me you should be able to call procedures from the DoWork and then pass updates back via the ProgressChanged event. I can't image you need to consolidate all your code into the DoWork.
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Jan 21, 2010
I am trying to do the following process in the method of BackgroundWorker.DoWork()
Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
For x = 0 To 100
[Code].....
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Jun 13, 2011
have a formthat hasa BackgroundWorker,on the do_work event i exe an SP:
Dim result As IAsyncResult = cmd.BeginExecuteNonQuery()
Dim rowCount As Integer = cmd.EndExecuteNonQuery(result)
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Nov 14, 2011
I tried to update the button text on a form from a backgroundworker.do_work event, and it failed, with the usual cross-thread exception message.However, by pure chance, I also tried to update text in a system.windows.form.toolstripstatuslabel also from this backgroundworker.do_work event, and it DOES work. Question: why is this? Is it perhaps because theres some kind of implicit shared behaviour with system.windows.form.toolstripstatuslabel?
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Oct 26, 2009
I am trying to execute the following line of code within the DoWork event of a BackgroundWorker object: [code]
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Jun 29, 2011
I am writing an application that calls data collectors (via ip or modem), collects data from them and reformats it. I had this much written when I was asked to make it multi-threaded so that I can collect from multiple sites at one time. I have that written using backgroundworkers and it appears to be working well. On my UI I have a text box that needs to update with status details like, dialing, collecting, reformatting, etc. I planned to simply write the status updates to the text box from an UpdateStatus routine. Found that had all sorts of nasty threading issues, so I added a delegate to call the status update routine. Problems seem to be fixed except that the updates to the UI are coming in chunks instead of one by one as they really occur. Can anybody tell me how to force the status update in the text box to update more asynchronously?
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Jul 29, 2010
I am trying to learn Background worker and have written up a very simple app to understand this process. My form has a
textbox and a label. When the user clicks on the button, it updates the label with the value that they have entered into the textbox(I know this can be done elsewhere in the code besides the dowork event, I am just
testing and learning). Please help..I am not sure what I am missing. The label does not update.
[Code]...
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Jul 10, 2009
I know the reason of getting this error" Cross-thread operation not valid: Control 'ListBox1' accessed from a thread other than the thread it was created on"
Is there any solution other than raising .ReportProgress event to update the form?
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Feb 22, 2012
I have a backgroundworker doing everything I want it to but I cannot seem to figure out how to get a listbox in the Windows Form to update from the worker. I have tried an number of things and have looked high and low, but I seem to be missing something. Is there a simple way to do this? here is a bit of my code:
[Code]...
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Aug 7, 2011
When it comes to Backgroundworker's, I just make a total mess, even after reading over and over again the Backgroundworker component info on the msdn site... I have a code I would like to run on the form but if I do it with a simple "Public Sub" it will make the form lag, freeze, until the operation is done. So I try to paste the same code into a backgroundworker, and use Runworkerasync, but I get errors stating that the backgroundworker can't access controls on the form.
[Code]...
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Apr 23, 2012
tion (even if it falls outside my form).I found some code to get the color.I would like to constantly update the backcolor of a panel to reflect the current color beneath the cursor until it is clicked.Here's an example of what I have tried (bwColor is the name of my backgroundworker):
VB.NET
Private Shared GetColor As Color
Private Sub bwColor_DoWork(ByVal sender As Object, ByVal e As
[code].....
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Jul 27, 2010
I have created what amounts to a progressbar which is launched using a backgroundworker. So all is well the main UI/process is doing its thing and the progressbar is ticking away. What I would like to do is update some text that is in the progressbar. So when the main UI/process finishes one of its tasks I want to update a message in the progressbar. NOT have the progressbar update the main UI/process but rather have the main UI update the progressbar.
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Feb 1, 2012
I'm seeing some strange behavior where the RunWorkerCompleted event for one of two threads I start isn't being called depending on how I call them. Check out the code below, and the two methods of firing the threads, good() and bad().
[Code]...
In both cases the DoWork event is called for both threads. But in the bad() case, only the second thread fires the RunWorkerCompleted event. This is obviously due to the two different ways I'm using VB to handle events here. I'm looking for an explanation of this behavior, preferably with a link to some documentation that could help me understand how these events are being handled in VB better. It seems strange to me that just reusing a variable name here seems to either dispose of the thread before it's done or else just make it stop firing events.
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Feb 9, 2012
I've started working with the backgroundworker class to try and keep the UI responsive while I make some expensive API calls. One of the API classes (details here[msdn.microsoft.com]) has its own event handler which I am using to update a progress bar in a small form that pops up. So I'm looking to use the PublishPackage command in a bgw thread and update a progress bar on the UI thread by using the ProgressHandler method.
[Code]...
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Jun 17, 2010
I am trying to display the progress bar(marque) in a separate form (progressForm) while i do some calculation in background. I know the typical way of doing it is to include the calculation in background worker and show progressForm in main thread. This approach how ever will lead to lot of synch issues in my application hence I am showing the progressForm using progressForm.ShowDialog() inside the background worker process. But I need to trigger the Completed event with in the application to close the form.
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Apr 10, 2010
I am trying to create a background worker that will spawn a dialog, while a long event is occurring. For example, when the main thread in trying to connect connect to a db and update a large amount of records, I would like to have the background worker spawn a dialog that advises the user to "Please Wait"
Here is what I have so far
1. I create a background worker using the drag and drop
2. Before the event that taking a long time starts I call:
Me.BackgroundWorker1.RunWorkerAsync()
BackgroundWorker1.WorkerReportsProgress = True
3. This is the events for the bgworker, all of which was enabled in the form designer:
Private Delegate Sub delCreateNewForm()
Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
Dim d As New delCreateNewForm(AddressOf CreateNewForm)
Me.Invoke(d)
[Code] .....
4. When the long activity is completed I call this:
BackgroundWorker1.ReportProgress(0)
Everything seems to work fine, except that the newly spawned dialog in no responsive and appears to be frozen, until its closed by the Progress Changed event.
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Jan 15, 2012
my current solution as you can see is by using shared variable within a class in order to pass a value.
on the form load of my application i called: workerSample.RunWorkerAsync
Dim finalList As List(Of String)
Private Sub workerSample_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles workerSample.DoWork
[Code].....
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Mar 10, 2012
I place some code below to simplify the process.
1) I am trying to use background worker to download a large file and update a progress bar to reflect the changes as the large 5GB file is being downloaded, and also update percentage completed to the label.text(lblInfo).
2) As I was goggling I came across some info that a web client is needed to calculate the maximum size of the file and divide by 100 and you can stream it down with the web client. Reading it is one thing, implementing it is another as I spent week trying to get it to work.
UCPocoAPoco
Imports System
Imports System.IO
Imports System.Diagnostics
[code]....
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May 22, 2011
I want to execute a few external apps, where in between a RichTextBox gets updated.. Say when program1 has been startet the RichTextBox is updated.. And when program2 has been startet the RichTextBox is beeing updated again.So what i've done so far is this:
Public Class Form1
Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
[code]....
But when doing the above i get the following error:
Quote:
Cross-thread operation not valid: Control 'RichTextBox1' accessed from a thread other than the thread it was created on.
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Nov 15, 2011
I have a VB.NET 2010 app that uses a backgroundworker to process MS Word docs. All of the code does what it is supposed to do, except when my code calls ReportProgress(). The UI cannot process the ProgressChanged event fast enough before the values in the class that are passed are changed. I know this because I inserted a System.Threading.Thread.Sleep(100) line after each ReportProgress() call which allows time for the UI to make the updates properly. I guess I am looking for a better solution thanThread.Sleep(100) since this adds to the amount of time it takes to process all of the files. Here are some snippets of code that I am using:
[Code]...
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Jan 26, 2012
I have build a VB.Net windows application which does uploads data into database and basically updates two controls:
1. A textbox which is constantly updated with one line per database record upload.
2. A label which keeps track of the count of database record uploaded.
I have used BackgroundWorker thread concept, where the thread's bgwWorker_DoWork() method contains the business logic for upload and bgwWorker_ ProgressChanged() updates the 2 UI controls based on uploads.But the issue I am facing is that I do not get complete updates on both the UI controls. Sometimes the thread bypasses update of textbox and sometimes of label. I could resolve this issue by adding System.Threading.Thread.Sleep(25) before each UI control update code.[code]
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Nov 16, 2011
I have a BackgroundWorker in a vb.net program that is doing a lengthy data import routine. I want to modify its RunWorkerAsync method so that it fires a custom event on completion of the method. (So that a method in an automated process can respond to the event and resume its work). In a sense I want to 'extend' the RunWorkerAsync method to add an extra line of code--but I can't 'see' the code in the method (to just add the line raising the event) because BackgroundWorker is an MSDN class from Microsoft.The only solution that I can think of is to 'wrap' the background worker class in a wrapper that calls the .RunWorkerAsync method and then raises the event.
Public sub wrapperMethod()
myBackgroundWorker.RunWorkerAsync()
raise customEvent
end sub
Is there a design pattern that I might use? An easy way to address this with the .net language?
PS: Unfortunately, I'm automating some clanking legacy software and backgroundworker is used in many locations, so wrapping the backgroundworker will be a bit of work and may open bugs.
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Apr 22, 2011
Objective to clear the datagrid view after updating. This should happen when the user clicks the OK button when the update is confirmed. Below is what i have.I currently have
Private Sub SaveToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles SaveToolStripMenuItem.Click
'This updates datsource
Try
[code]....
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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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Nov 9, 2010
I am trying to get a progress bar to update on my Form while waiting for a process to complete but could not get my progressbar control to update.
First of, I have tried to fix the problem for a day and a half now looking at various codes and examples in the forums but I'm afraid I probably do not have the necessary VB skills yet to troubleshoot my own code. I believe I will be able to eventually fix this after I am done with my VB book
I've attached the relevant part of my code below and the problem is that I can see my DoWork event firing off and changing the time and percentage that I want to pass on to ReportProgress() and the ProgressChanged handler. However, the ProgressChanged handler is not raised until after my Do Loop is done.
Imports System.ComponentModel
.
.
.
Public Class Form1
Private WithEvents TestWorker As System.ComponentModel.BackgroundWorker
[Code]....
Again, I can see the ProgressChange fire but only after my work (diagnostics) is complete so my progress bar is either 0% or 100%. In Dowork, I can verify that the progtimepercentage variable is indeed changing and ReportProgress is called but ProgressChanged is not being raised until after the job I wanted is done.
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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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Mar 1, 2012
I'm getting frustrated on how hard it is to find a good DataGridView event, BindingSource event, or DataTable event to use to update my database. I have to use a stored procedure to do my adapters update, because when a user updates a row
I have to check for concurrency to ensure 3 other related rows to the row that has been modified hasn't been updated since the user obtained the data. For example, if my query returns 4 records and the user updates the 4th row, I have to ensure rows 1-4 haven't been updated since the user retrieved the records.
My DataSource is a DataTable and I use a BindingSource to bind it to a DataGridView. I want to update my database whenever a user changes a cell value in the DataGridView or when I change a value programmatically to the underlying DataTable. Anyone recommend an event from any of these objects?
The problem I'm having is this. When the user changes a cell in the DataGridView I want to apply a date time stamp in another cell in that same row before I update my database. If the update is successful for that row then I AcceptChanges or if it fails then I RejectChanges for that row. I can't change any values in the row in the DataTable RowChanged event because it will be an endless loop, plus it does fire when the user changes a cell. I can't use DataGridView CellEndEdit because when I change a cell value programmatically using a loop the event won't fire to do the update. I can't use DataTable ColumnChanged event because the row hasn't been set Modified so the adapter doesn't know to update the row.
What do the experts recommend?
CODE:
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