Getting Backgroundworker To Work?
May 23, 2011
I have not used Backgroundworker before and this one has me stumped. I have run examples (this is based on one from MSDN) and read what I could find, but I just can't seem to make this work. I am sure it is something simple that is wrong with my code, but don't know how to go about troubleshooting it. What happens is that it goes to the startthread() sub dim the object and sets the two variables and then bypasses the last line that starts the worker process. I'm stumped.
Here is the original code that works just fine, but hangs up my app (hence the need to run a background process)Above the is an Imports RARNET to support this:
[Code]...
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Aug 21, 2011
this is my code:
Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
For i = 0 To 1000
[code]....
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Jul 21, 2011
Do you know how to work backgroundworker with this code? The request would be as I pulled out of google with a background worker and if so it is possible to collect links from google pagination.
[Code]...
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Dec 2, 2009
I'm using the IsBusy property to determine when a backgroundworker has completed. In the RunWorkerCompleted event I assing the result of the RunWorkerCompletedEventArgs to a public variable within the module where the backgroundworker events reside. The trouble is, the IsBusy property occasionally becomes true before the public variable gets assigned the value of the RunWorkerCompletedEventArgs. I experimented with putting a Threading.Thread.Sleep(10) after the IsBusy property becomes true and it seems to fix the problem. But it really doesn't seem right that I should have to do this. What is wrong here? I have placed the backgroundworker events in a component that is instantiated from the windows form, instead of placing the background worker events within the code of the form itself.
Here is my code;
Function SendAndWait(ByVal IntegerArray() As Integer) As String
Component.BackgroundWorker.CancelAsync()
Do While Component.BackgroundWorker.IsBusy
[code]....
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Apr 14, 2011
I have a long running process running in a backgroundworker, and want it to report progress to the user, and update a checked listbox as the items are discovered. The reportprogress is called, and the statements executed (placing a break in the reportprogress routine), I can see the control valuse change, but the change is not reflected in the dialog. Here is the reportprogress routine I'm using:
Private Sub BackgroundWorker2_ProgressChanged(ByVal sender As System.Object,
ByVal e As System.ComponentModel.ProgressChangedEventArgs) Handles BackgroundWorker2.ProgressChanged
Me.newlabel.ForeColor = Color.Cyan
[code]....
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May 24, 2009
i want to use the following function
Dim
buffer() As Byte = System.IO.File.ReadAllBytes( ImageSourcePath)
inside a backgroundworker but it does not retunr any byte at all while if this is places outside the backgroundowrker it works files.
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Mar 27, 2012
I have a UserControl that has a ProgressBar on it. The purpose of the UserControl is to be able to show the progress % on the ProgressBar as text. To do this it uses the MyBase.Paint event. To make it work the ProgressBar is made invisible and the UserControl is 'painted' with an image of the ProgressBar and then the text is painted on top. The UserControl has a Value property that is passed through to the ProgressBar.Value property.
I use this UserControl in two places, on a Splash form (not a standard Splash Screen) and also on the main form of the application. It works on the Splash form but not on the main form - by work I mean that changes to the ProgressBar.Value property cause the ProgressBar to show its progress. The cause appears to be that in the Splash form case the MyBase.Paint event is called as a consequence of calling Me.Refresh in the Set procedure of the UserControl.Value property, in the main form case it isn't,
i.e. Me.Refresh isn't causing MyBase.Paint to run.
The main form has two BackgroundWorker components. The first gets called (RunWorkerAsync) from Form_Load after the Splash form has been shown. The BackgroundWorker.ProgressChanged event updates the Value property of the UserControl and it works exactly as intended. The second gets called as a result of a user starting an operation and again the BackgroundWorker.ProgressChanged event updates the Value property of the UserControl but MyBase.Paint doesn't run so the ProgressBar remains resolutely static.
Any ideas why it won't respond to Me.Refresh in one case but does in the other? Happy to make any of the code avaialble but didn't want to fllod the first post with reams of it. Here's what I think are the most relevant code sections. First the UserControl
[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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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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May 29, 2012
I found that when group by multiple values does not work well with VB.NET, but it works well with C# ,here are my code, is there something wrong with my VB.NET Code? Here is my VB.NET code:
[Code]...
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Feb 2, 2011
I have an application that requires data be entered, and after entering, a button is clicked to process that data. Clicking the button works just as it should--the data is processed properly. In constructing a test module, I provide a set of data values, followed by:
btnWhatever.PerformClick()
Nothing happens. I have used this syntax for years, and it has always worked flawlessly. I have triple checked everything else and isolated the problem to the failure of the PerformClick(). The PerformClick() is in a test subroutine that does nothing but fill textboxes and labels with default data, then calls the PerformClick() on the button to begin processing. Again, the button works fine, the data is entered as it should be, but the PerformClick() does not fire the click event.
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Aug 21, 2009
I have a form that works on my local Machine I created into. I have Office 2007 on this machine. I created the Form with the Excel 12 Reference. I move the Entire conetence of the Project folder to my work computer. Which has Office 2003. Do I need to recreate the form with the Excel 11 reference. I could not get the form to work on work computer. IT has a com error. I am acessing the EXE for the debug folder w/in the Bin Folder.
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Jul 25, 2010
will SQL statements that work in Compact SQL Server also work in the Express Edition of SQL Server?
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Jun 21, 2010
good example on backgroundworker control in vb.net for doing some process in background for ex a reading a doc file in textbox by using backgroundworker in vb.net?
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Jan 29, 2011
Is it possible to set a backgroundworker as STA
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Nov 9, 2009
what is this BackgroundWorker and how to use it? Can it be used as a replacement to System.Threading.Thread??
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Sep 8, 2010
I've got a bit of a problem, I'm using a backgroundworker to do a lot of processing and it adds items to a listview with: AddListItem(ListView1, listItem)
Here is the delegate code to send the command to the listview outside of the thread:
Delegate Sub AddListItem_Delegate(ByVal [ListView] As ListView, ByVal [text] As Object)
Private Sub AddListItem(ByVal [ListView] As ListView, ByVal [text] As ListViewItem)
[Code]...
The problem is, as you might imagine, flickering of the listview. Can anyone help me out with a solution to execute a LockWindowUpdate(Me.Handle) command in the backgroundworker? I've tried creating a new delegate but it's not working (errors, I don't understand vb.net enough).
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Mar 11, 2011
I am programming using VB.NET 2005. I am using a BackgroundWorker to load a large list or text file and process it.
Is it possible to use the same background worker to process something else, i.e. to process the text file that was loaded? somthing like
Dim bwkMain as New BackgroundWorker()
If its possible, how do I implement it in the same form as I have already implemented for the first one?
EDIT The question is: is it possible to use the same BackgroundWorker for another task, after it finishes one task?
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Mar 21, 2011
I have limited experience in VB.net and have become stuck. I have tried to search for answers on other threads without success.I have an application that displays real time data.Queries are made to a MySQL database on another PC over the internet every 10 seconds to gather the most recent data.I have done the query within a BackgroundWorker so that the GUI is still responsive while the query is answered.What I've done works great for several hours or maybe for a couple of days but then the DoWork task appears to hang.
The code I'm using is to run the background worker is:
vb
If Not(backgroundWorker1.IsBusy) Then Me.backgroundWorker1.RunWorkerAsync() End If
The backgroundWorker runs just once and there's very little code in the DoWork routine:
vb
Private Sub backgroundWorker1_DoWork(ByVal sender As Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles backgroundWorker1.DoWork rs = New
[code].....
Is there anyway I can set up a timeout on the maximum allowed time that the DoWork task can be active for? And if so how would I then go on to stop the backgroundWorker?I understand that CancelAsync isn't going to help as my DoWork task is not repeating as it runs once only, then stops and 10 secs later I run it again.
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Jan 24, 2009
I'm trying to add a backgroundWorker to my application, but I can't find it.I tried looking in the toolbox, but didn't find it. I looked in the Choose items dialog box and it is checked. Tried unchecking and checking it again, no difference.
I tried using Dim worker As System.ComponentModel.BackgroundWorker but get an error:
Type 'System.ComponentModel.BackgroundWorker' is not defined.Is there any way to add it to my program?
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Jun 26, 2009
I used sample from jmcilhinney at Link to create background proces and it works like a charm. But. In my menu i have two (2) different toolstrip buttons which i need to run the same BackgroundWorker1_DoWork method, but different ackgroundWorker1_RunWorkerCompleted methods. Is that doable?
1. In BackgroundWorker1_DoWork method i use some time-consuming operation which at end sets two global variables.
2. In BackgroundWorker1_RunWorkerCompleted method I use some Select case statment based on that two global variables that are not the same for ToolstripButton1 and ToolstripButton2.
Vb.net
Private Sub FirstButtonToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles FirstButtonToolStripMenuItem.Click
[code]....
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Apr 27, 2010
Imports System.Net
Imports System.Text.RegularExpressions
Public Class Form1[code]....
This is my code, and it doesn't work. I can't see a results in TextBox.
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Feb 21, 2011
i'm trying to do a database search in my WPF program. And to give the program some speed, I want to use Backgroundworker or Threading. The problem is that i have to invoke the controls that the new thread is going it access. But i don't know to do this and i don't know i which event to put the code. Here is some code:
[Code]...
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Jun 19, 2009
I am building an app that connects to a webservice that returns an XML file, and due to the lag I want to use a backgroundworker to connect and then return the data when its done, and also store the cookies in CookieJar so I can use one post to log in, and get the webservice to auth the session. However, I am completely stuck as I cant get BackgroundWorker to return anything other than a true or false when it completes. I am used to PHP now, until a few weeks ago it had been 5 years since I last used VB ( and it was vb6) so I am rusty.
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Sep 19, 2010
I cannot make it work. I'm a beginner, and not being sure what's really relevant I'll say I'm using VS2010 Express edition, on Windows7 Pro 64 bit.It's been bugging me for days, and I even thought it was because I was using Express edition, but it wasn't. I copied their Fibonacci example, and it worked as expected. Meaning: progress bar reported progress, GUI was responsive, so Cancel button could have done its part.
But I didn't want Fibonacci calculator, because recursive calls always make me think about stack overflow. I wanted something less fancy; I wanted simply to count to 100.000 and see the counter on the GUI changing all the time.So I followed the instructions on their Fibonacci example, but I made it only count "in its mind". It updated progress bar all the time, but text box shown only the last result after finished counting. Also GUI wasn't responsive, so I couldn't click cancel button.
When you start Fibonacci example, you could move the form around. But in my case, GUI was frozen, and form was moved only at the end of counting.
[Code]...
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Apr 19, 2011
I have an applictaion with a DGV which has many rows> I need to make different formattings depending on values from some columns. I was thinking to use event CellFormatting but it takes to much time. So, the other solution shoul be to use a backgroundWorker which will take care about formatting dgv.
Unfortunatelly I do not know exactly how to do that. I have tried in many ways but I have received the message:
Cross-thread operation not valid: Control 'StatusStrip1' accessed from a thread other than the thread it was created on.
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Jan 29, 2009
how can i use BackgroundWorker in a module
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Apr 10, 2012
I have a job object for long running operations that works like this:
[code]...
This worked fine a year ago, and I moved on to other things. I had to return to this code today, and when I run it now, the OnDoWork override is simply not called. A breakpoint in there isn't hit, debugging messages aren't written, the method is simply not called, and no errors are thrown anywhere. I can't think what would have changed that could cause this, since it seems like a low level framework thing. The rest of the app loads and runs fine, the main window shows (it's a WPF app), and button click events fire. It's just the background thread method that doesn't fire. What could be going on here?
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Jan 23, 2012
I have problem in my application to access a picturebox from a thread to make it visible or not.
When I try to change visibility from the thread, i get the above error, if i disabled crossthreading exception:
Me.CheckForIllegalCrossThreadCalls = False, the program run normally with no error but the image still not visible after i click the button (Start the thread and make picturebox1.visible = true)
change the visibilty of the picturebox from a thread (Backgroundworker).
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Sep 8, 2010
I'm using a vb.net backgroundworker thread for processing and I need to periodically add items to a listview (with multiple columns) during the thread processing.I can easily use the following code for delegating the task to add an item to a listview, but I can't figure out how to additional info to other columns on the same row.he thread, I'd execute the following to trigger the invoke to add to listview:AddListItem(ListView1, filepath)Here is the delegate code, if someone can show me how to add the t
Delegate Sub AddListItem_Delegate(ByVal [Label] As ListView, ByVal [text] As String)
Private Sub AddListItem(ByVal [ListView] As ListView, ByVal [text] As String, Optional ByVal [text2] As String = "")
[code].....
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