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.
I have a search box that works great in WinForms, but is giving me trouble in WPF.
It works by starting a search each time a letter is pushed, similar to Google.
[Code]...
Is it possible to send information to a BackgroundWorker thread while it is running? Here is my scenario: Parent thread calls background thread to send a data request to a database. If it's a big complicated query it can take a while for the db to respond, so putting the db request on the background worker thread is great. My app can do other stuff while the one thread waits for the db.
Now, db responds with beginning of data. I want my background thread to report back meta data about the result set to the parent thread. No problem there, I can use a custom user state object and the ReportProgress method. But now, how to I send a signal from the parent thread back to the worker thread? I want the background thread to wait while the parent thread does something, and then tells the worker thread to keep going or quit. I know how to cancel a background thread, but I want the parent to be able tell the child some information other than "cancel". Here's one way to think about it:
[Code]....
I'm using a BackgroundWorker to perform some analysis on a separate thread. The BackgroundWorker is called when a user clicks a CheckBox.
I need to provide for the user clicking the CheckBox, starting the BackgroundWorker task, and then changing their mind and clicking the CheckBox again.I simply want to cancel the currently running task and set the analysis off again. Currently I have the following method:
Public Sub UpdateParkStatusAsync()
Try
'Debug output.
Console.WriteLine("UC_Map_ViewModel.UpdateParkStatus called.")
[code]....
I am writing a project in Visual Basic where I need to run several instances of the same method in parallel. I can do this using BackgrooundWorker by having several (4) copies of my code module (modules 1, 2, 3 and 4) with a call to background worker in each. I then have a Main form which invoke the 4 modules which setup 4 simultaneous background threads. Seeing as the code is the same I want to simply invoke the same module 4 times.
However when I do this I get an error from Backgroounworker that it is already busy. As I understand it this means that it is being shared. However, I have specifically instantiated it as "private" (private with events worker as new backgroundworker). I have tried running the same code in a Class instead of a Module but unless I make it public I have no way of invoking it from Main. I need to be able to pass each thread data from main for it to work on and if the class is private I cant invoke it.
After searching thru BOL and various forums, I've been unable to determine how to use a backgroundworker component with a procedure that contains multiple parameters. If I understand correctly, DoWorkEventArgs is used to pass parameters. However, all the examples I have found use only one. Since DoWorkEventArgs ends in an "s", I imagine it is possible to use more than one parameter.
View 3 RepliesI need to run multiple task in the background using backgroundwoker
e.g dim mybacgroundwokers(10) as backgroundwoker
in the backgroundworker event procedure, can i do somthing like this, cos i don't have an idea
mybackgroundwoker_dowork(,,index)
select case index
case 1
'dowork for backgroundworker1
case 2
'dowork for backgroundworker2
end select
or how do i handle multiple backgroundworker if non of this is possible with the backgroundworker, how do i do this using thread multithreading?
I have an app that is needs to access multiple web sites and sign up for accounts. I don't want to run them one by one as this would be slow as christmas so I figured that I could setup some sort of background worker and put each process on it's own thread that way the app could run each sign up page at the same time. Would using background worker be the "BEST" option to use for this type of application requirement?
View 1 RepliesI have been pulling my hair out trying to get this to work. If I step through the code in debugger it all works great. My problem is if I just run it, only the last task responds. I'm guessing I am overwriting the background working or something. I am sure I am doing a few things wrong but my code is now messy as I tried many way while searching. I know of the threadpool and .Net 4.0 tasks but having a hard time getting to do what I need.
Basicly I am writing a program (trying more likely) that takes a list of computers and pings then, then checks their uptime and reports back.This works fine in the UI thread (Obviously that locks up my screen). I can have the background worker just do this, but then it does each computer 1 by one, and while the screen is responsive it still takes a long time.
So my answer was to have a for loop for each server launching a new background worker thread. My solution does not work.I have seen other threads that I could do it, but I need to use with events to call code to update to UI when each is done.
What is the most simple way to do this?
Here is my code. Most is just copy paste + modify till I get it working right.
So In the main class I have the testworker.
(I tried using Testworker() but it said I could not do that WithEvents)
When I click the button the list loads.
Private WithEvents TestWorker As System.ComponentModel.BackgroundWorker
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.Windows.RoutedEventArgs) Handles Button1.Click
[Code]...
I'm running in to a problem that I was able to fix with Application.DoEvents, but don't want to leave that in because it might introduce all sorts of nasty problems. Background: Our app is primarily a desktop app that makes many calls to a web service. We control everything but changes to the overall system design are not going to be seriously considered. One of those calls, Calculate, is used very often, and occasionally can take a few minutes to process all the data to return valid results.
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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.
View 11 RepliesI 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?
View 4 RepliesI 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?
I have a search function in my program that uses a background worker in order to get the results. The Progress changed event is used to update the listview with the new item.[code]
View 2 RepliesI cannot figure this one out.. I have a background worker that will perform a task streaming data from some webpages. this data is then passed back and displayed in a gridview. It has been working fine.
I've recently implemented a listbox, which its values will be passed into the function that the background worker will perform as parameters, originally i had taken a single value from a textbox.
Now, I thought maybe it had something to do with the listbox, so I used a static value, just a simple String, as the parameter, and again, I get the TargetInvocationException was unhandled.. There's no difference in how I perform the task I'm trying to have the backgroundworker complete, the only difference is where it exists in my if condition statement:
Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles ScrapeSites.DoWork
Dim results As ArrayList
Dim worker As System.ComponentModel.BackgroundWorker = DirectCast(sender, System.ComponentModel.BackgroundWorker)
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I have a project in VSTO/VB using a BackgroundWorker that works fine. It is a form that calls for a web page of information. The web page can take a while, so I have the form calling with the BackgroundWorker.I then have an Excel Addin project that has added the BackgroundWorker project. When I call up the form from the Excel Addin project and use the BackgroundWorker to request the web page, it grabs the web page ok. But the work done upon completion, during the BackgroundWorker1_RunWorkerCompleted method, is resulting in an error message:
View 2 Replies[Code] This is run from inside a backgroundworker. It throws an error, Cross-thread operation not valid: Control 'pbUpload' accessed from a thread other than the thread it was created on. I have read and read and searched and basically come to the conclusion I am going to have to invoke the command but this is new area for me.
View 5 RepliesI am using a background worker's work method to create a new form and show it.
But it throws this error
System.Threading.ThreadStateException was unhandled by user code
Message="Current thread must be set to single thread apartment (STA) mode before OLE calls can be made. Ensure that your Main function has STAThreadAttribute marked on it."
[Code]....
I have a backgroundworker that is downloading data from different webpages and process them to a datagridview.I get the Cross-thread operation not valid error on the first For loop.
Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
dim i as integer
tot = (numPostnrTo.Value - numPostnrFrom.Value) / 10
[code]....
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?
View 1 RepliesI'm writing something to download about 200 small (Around 200kb) files at a time. I pass the file urls off to a class which starts the downloads. The problem is that it'll start the download (Just creates a 0kb file) and then slowly downloads each file one by one, waiting for the next to complete despite this being a threaded class. This would be fine but after about a minute, windows removes all of the 0kb files and I'm stuck with only a few of the files being downloaded. How to get multiple files to be downloaded concurrently?
Imports System.Net
Imports System.IO
Public Class DownloadClass
Public downloadUrl As String
Public folderURL As String
[Code] .....
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?
View 2 RepliesIs it possible to set a backgroundworker as STA
View 1 Replieswhat is this BackgroundWorker and how to use it? Can it be used as a replacement to System.Threading.Thread??
View 2 RepliesI'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).
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?
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.
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?
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]....
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.
