BackgroundWorker And CookieJar?
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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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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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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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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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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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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Aug 3, 2011
I'm trying to load data from DB with a BackgroundWorker but I'm getting the follow error:
Quote"Cross-thread operation not valid: Control 'DataGridView1' accessed from a thread other than the thread it was created on" Well I didn't created any other thread or call it from other place, my code is just:
[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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Jun 30, 2009
I can't seem to find a good tutorial on how to access uithread components from thebackground thread.. It seems like there is different means of accomplishing this
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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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Jun 21, 2010
background worker is not executing all the code in side it. windows application..Although there is not any exception.
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Jan 6, 2010
I am using backgroundworker thread in my app. I also have a class in my project and am able to updated the user UI from the form, but most of my time consuming operation happens in the class so I tried to do an update like this Form1.BackgroundWorker1.ReportProgress(4, strname), but I get an error that say that the backgroundworker is not set to report progress.
I have this set in the load event for the app.Are you not able to call form items like this from a class?
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Aug 26, 2010
When using the backgroundworker, I know that the DoWork event is not suppposed to support cross thread operations for controls. I have a public integer variable declared on a different form that I need to test in the DoWork event.The backgroundworker seems to not be able to check what the variable is, as the test never enters inside the if/end if check. If I copy the code exactly to a different sub (IE, not a background worker, a normal sub) and call that sub instead of starting a background worker, the if/end if always gets entered.I'm confused as to why it won't raise a cross thread exception, but won't test the variable that makes the check true (as it does in the test sub).I added in a try/catch block and that doesn't catch any exception either. I tried a timer and started the new sub with that timer, but that still completely locked up the app...
[code]...
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May 2, 2009
I am using a class with below code, the question is how to update the label's value at UI thread from the backgroundworker?
Imports MySql.Data.MySqlClient
Public Class clsBackGroundWorker
[code]....
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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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Dec 22, 2009
I am using BackgroundWorker to connect asynchronously to a database. Private Sub frmMain_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
[Code]...
While my connection is being opened, I have a "Loading" animation show in a lblCalibration. Once it's connected, the animation stops successfully and shows the calibrated record that I am fetching from my db.
However, if there is an error while connecting to my db for any reason, it does not work. My app freezes. The reason is because I am trying to make a cross-thread call while trying to Catch the error in the DoWork event.[URL]..
but still cannot seem to make any progress. Does anyone have any tips or advice on how to properly catch the error and still run BackgroundWorker?
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