.net - Why Isn't BackgroundWorker.OnDoWork Getting Called
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?
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.
i was wondering if it possible to have a condition where lets say you have a column in the datatable called amount and a textbox acting as the filter called say maxamount to set it so the rowfilter when filtering the table will sum the number in the amount column until the number in maxamount is met, then stop and only return the rows where the total sum of the amount column is equal or less than the maxamount value, so i guess if the next row takes us over the maxamount it discards this row and returns the rows previous to it. is this possible using datagridview rowfilter or should i be loooking elsewhere to achieve this?
I have an sql table called Stock with two fields called StockID and StockCode. I want the user to select the stockcode from a combo which in turn populates the stockid for that item into a lable on my form. I have already populated the stockcode into the combo but dont know how to compelte the rest.
Imports System.Data.SqlClient
Public Class cbo2 Private Sub cbo2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
I have a form called FrmPracDetails which is built up with a List view called LvwColProc. Therefore when you click a field on the LvwColProc it takes you to another form called FrmColProcessing, here you can make changes to certain fields which are also present on FrmPracDetails. What I want to do is when you make changes on FrmColProcesing and Click the Save Button (which calls the Save function)the changes appear instantly on FrmPracDetails. Please note, FrmColProcessing will always be open next to FrmPracDetails. I have tried to put this code in the Save function present in FrmCol Processing as shown below, but it doesnt Refresh FrmPracDetails form. [code]
This JCL_History object is basically a Generic.List encapsulated in a wrapper and has the following method:
Public Sub Enqueue(ByRef value As String) If Members.Contains(value) Then Me.RemoveAt(Members.IndexOf(value))
[Code].....
In my testing I have 2 items in this JCL_History list. When I call that first line of code I posted (the one that invokes Enqueue) with I = 1 I expect the first item to be shuffled to the bottom and the second item to be shuffled to the top.
After the thread returns from Enqueue I notice that this is exactly what happens to my list, HOWEVER if I hit the "step_in" button after the execution of Enqueue I go into the Default Property's set method where Index = 1 and value = and it screws everything up, because the item that got shuffled to the end (index 1) gets overwritten by the item value shuffled to the top.
So basically the set method on the default property is getting called at what I think to be a completely ridiculous time. What gives? By the way I'm running VS2005 on XP.
Can you look at my coding and let me know what I'm missing or doing wrong?I have a SSRS report that is called from a ReportViewer control and the ProcessingMode for this control is Remote. The report also has 1 parameter in it's DataSet.In the code I placed a MsgBox to make sure the code is finding the parameter and returning the parameter name. I am trying to stick the value of 10 into the parameter for playerID 10. Data for this player does exist.
I believe I need to add some more code to make this work but I'm not sure what else to add.
When the code executes the report is displayed but no data is shown in the report.
I recently found an awesome tool called "Freemind" that is called a 'mind mapping' program. It's similar to MS Visio but way cooler and more automated.I reeeallly would like to integrate this into a VB.net Form, but how?
Has anyone seen or heard of mind mapping inside VB.net before? Are there programs out there already that work with VB.net or anyone have an example they have seen / built that works?
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.
My code Adds a New Row from a Source Table called "objTablaOrigen" To a final table called "objTablaDestino". This tables are passed ByRef because they come from a DataSet respectively. objRowNuevo is The Row that will be added to "objTablaDestino" The data from "objRow" is well copied to the "objRowNuevo" (that is the new Row with type of objTablaDestino).
'The problem occurs when the instruction Add is executed. ¿What happens? The new row is added as well, but this generates an Exception with the next message:
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?
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).
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
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:
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.
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.
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.
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:
in the .net dll (named "Calendar") I have a public class called clsCalendar that has several public properties and functions. In the Calendar project properties I have checked "Register for COM Interop" on the Compile tab. Also on the Application tab I clicked the "Assembly Information" button and selected "Make Assembly COM-Visible".
I have tried every tip/idea I can think of that I stumbled across such as running sn.exe and then in the Signing tab of Calendar properties checking "Sign the Assembly" and picking the .snk file created from running sn.exe.I have tried running "Regasm.exe" against my Calendar.tlb file with the /Codebase option. Nothing seems to work.When testing in a .net app, I needed to code as "new Calendar.clsCalendar" to get it to work. Our existing vb6 apps that need to call the dll simply say "new clsCalendar" and I can't change these apps.
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).
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 = "")
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:
