Make Sure 'ProgressChanged' Event Executes Completely Before Executing 'RunWorkerCompleted' Event Of Background Worker
Sep 20, 2010
Starting from my understanding about Background worker control, I understands that the background worker runs the code in its "DoWork" method in a seperate thread, while ProgressChanged and RunWorkerCompleted events are executed on the main thread.In my senerio, I report the progress and under an specail condition my application displays a message box to the user in "ProgressChanged" method using MessageBox.Show(). and in "Run Worker Completed" event the application finalize some work. There the sequence is important, suppose that the message is of Yes or No type and finalization depends on it. Now when i run my application, the background worker triggers "ProgressChanged", but as soon as backgroundWorker's cancelAsync() is called the program leaves the current "ProgressChanged" method and executes "RunWorkerCompleted" code first.How can i make sure that the "Run Worker Completed" code executes only after the completion of ProgressChanged method.
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Apr 23, 2009
I have a windows application that need to process som quite time consuming jobs. In my first try i did all processing under
the form thread. The result was bad response and update of the form due to the heavy jobs.To get around the problem with bad response from the form i created a new class "processing" where i put all the data processing. Then i instanciated a background worker where i in the "doWork" sub created a new instance of "processing".The "processing" class creates a timer from system.timer, and the timer drives the processing.On the Timer event Elapsed the timer starts a new thread from the thread pool.
My problem is now when i want to asynchronously close the background worker (with the corresponding function call what ever it is called ...) there is still a timer thread out there that causes exceptions for me.
1. How can i close my background worker and at the same time have the timer to be stopped?
2. Is there a way to synchronize the timer event so that the timer executes from the background worker thread?
3. Is there a better approach for me to adapt?
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Nov 20, 2008
I have a background worker that used to fire its RunworkerCompleted event when its DoWork routine finished querying a database and writing its output to a file. The bg worker was in a class called Query, which was called from another class called Trigger. A new Trigger Class was created for each monitored event. In this class, there was a structure which stored the config of each Trigger. When this event was triggered (set to TRUE) a new query class is created and it is passed the Trigger class. When the database query, file writing was done, the query class and all its rsources were diposed from the RunWorkerCompleted EventRecently I changed the application so that a new trigger class is not created for each monitored event. There is a single instance of the class but new config structure for each event. When a particular event is trigger, jsut the config structure is passed to a new query class and the sma ething is done in the query class. I just noticed now that the RunWorkerCompleted event is not being fired anymore.
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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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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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Jul 8, 2009
First, I launch a website in Internet Explorer from VB.net and automatically login the user with ther username and password. As soon as the username and password fields are automated, I send "enter" to the website so it goes to the next website. This part works perfectly. However, my problem is that i want to send a mouse click event, which i have already written, to click a hyperlink on the next website page. I tried a few different things, none of which worked. My program is automatically logging in the user and doing the mouse click event at the same time. I have tried to use the "sleep" command, but the mouse click event is still not executing after the second webpage loads. I have tried using nesting "If, then" statements and that has not worked either. Does anyone know how to make sure the webpage fully loads before executing a sendkeys routine or a mouse click event? This is my code thus far:
If (Search.ComboBox1.Text = "IWR") Then
BlockInput(True)'this disables the mouse and keyboard
Dim IE As New Object
[code].....
There are no errors, everything is just executing all at once instead of letting the second webpage load and then executing the mouse click event.
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Sep 23, 2009
does anyone know why the form load event being completely ignored/bypassed during loading the app? The form loads but none of the code in form_Load sub being executed (yes I tried putting a break inside the sub and it didn't trap)
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Jun 23, 2011
First, Im new to VB but have been programming for 20 years.
Ive been creating an application that starts with a form that has 4 text boxes with corresponding search buttons.You key something in to one of the text boxes and click the corresponding search button and it would execute the code in the button click event. It worked.
Ive done something though to make it not work.When I run it and click on the button it doesnt run the click event.
If I double click on the button in the development mode, it should, I thought, go to the click event in the code but it doesnt.It creates a new click event with the same name as the original but with a_1 appended on to the end of the name.
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Oct 28, 2010
I have a form that I call from another form. Whenever I call it using form.showdialog() or form.show() the form appears, but it never executes the code that is in the form_load sub.
What's the deal? I call other forms in the same manner and they all load and execute the load code without issue.
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Aug 2, 2010
I have created a class, in which button control is created programatically. The click event is added using "Add Handler". Now I create an instance of this class whenever I want to create a new button. The problem with this design is that in the ButtonClickedevent I have to write swtich cases to provide different implementations as per requirementI don't want to perform this functionality in this class. Is there any way in which when I click on this button the method from other class gets executed? may be inheritance,
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Feb 15, 2011
I'm writing a command-line application in .Net. The app itself is fairly simple, but it has to connect synchronously to a web-service, which in turn has to connect to a Oracle database, and those pieces are fond of taking their time.
Is there a straightforward way (without dividing my app exe in two) to continue executing but nonetheless yield execution to the command prompt?
It's Windows, so no "&". Also, I cannot use cmd.exe's "start" cmdlet.
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Mar 11, 2009
I have the following code that adds a background worker into a VB.net WPF project:
Imports System
Imports System.ComponentModel
Imports System.ComponentModel.BackgroundWorker
[Code].....
And I get the following error for the DoWork worker event:
Handles clause requires a WithEvents variable defined in the containing type or one of its base types.
It seems like it's missing something in the Event declaration, but can't find it.
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May 17, 2010
I don't know why this is. I am using VB 2008.net and I am trying to receive data on the serial port.
For some reason, the following event is not executing. Here is the
[Code]...
Just simple as of right now for debugging purposes. I have a breakpoint at getMe and it doesn't hit it at all. I know for sure that the serial port should be receiving data as I am using RealTerm to monitor serial port input data before I run my program.
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Jul 31, 2010
I've read thru Iceplug's tutorial on control arrays and got it working. I tried to add a new event by basically copying his click event code and calling it a doubleclick event. I used the proper addhandler and assigned the correct name to my sub. I have the click event changing the background color to blue and the doubleclick event changing the background color to green. The background color does not change to green. Why?
Heres the tutorial with my new code encased in asterisks ...
Code:
Imports System
Imports System.Windows.Forms
Public Class form1
[CODE]...
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Feb 24, 2009
I have some difficulties concerning threading [code]
Code:
1- Dim str As String
2- Dim x As New myClass
3- str = x.doSomething()
4- x.closeSomething()
I've included line numbers so I can just refer the lines by their numbers. My problem is, when the program executes, line 4 seems to be executed earlier than I want it to. It gets executed while ThreadX is still running in line 3. How can I force the program to wait until ThreadX has finished executing, before it executes line 4?
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Mar 30, 2009
I am using VB.NET for Windows applications. What is the difference between Load event,Activate event and Enter event in the Form and in which order the above event is executed.
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Jul 20, 2010
I'm trying to validate a few things in a form I'm building. It has a datagrid with clients info (taken from an access database) and a few textboxes where the user can type some search criteria. The thing is that those same textboxes are used to add new clients to the database and to modify a client's information if one from the datagrid is selected, so I made it that the buttons to insert and modify clients are disabled on load and thenevery time the text on a textbox changes ("TextChanged" event) they become enabled. So far so good. But then I wanted to make it so when a client from the datagrid is selected both buttons become disabled again until the text on a textbox changes (to make sure they're adding a different client and not the same one that was
selected).
I tried using the CellClick event from the datagrid to disable the buttons, but since every time a client is selected from the datagrid the info is shown on the textboxes, this triggers the TextChanged event too, and the buttons become available.So, is there a way I can tell the TextChanged event not to be triggered when the CellClick event occurs?
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Apr 4, 2012
I would like to know please how to check whether a string exists or not in a html code. I'm executing a for loop. Each time it checks a different url, so I want to be able to check each time if for example "<img" exists .
P.S: What's the difference between using
webrowser1.navigate
AND
dim request webrequest
request = WebRequest.Create
etc...
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May 3, 2012
I am using query from a SQLite database as the AutocompleteCustomSource for a ComboBox. Also, I want to load data in separate thread. My LoadData method works fine when called directly, but it fails when it is called from the BackgroundWorker thread. When it is called from the background thread, it throws a Specified cast is not valid exception on the csearch.AutoCompleteCustomSource.Add(hh("Taj")) line. Below is my code:
Sub LoadData()
Dim connetionString As String
Dim cnn As SQLiteConnection
[Code].....
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Aug 29, 2009
How do I fire an event from a background thread I created onto the main thread in a class in vb.net?
I've searched A LOT fot this, but could only find non vb.net examples, mainly C#, and have not been able to translate these.
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Feb 26, 2011
i am trying to create an application like a media player....Say i got an option which changes the background image of the form,like skin or something!now i want to change the mouse events when that background image is active on the form... lemme give u an example of a code...
Private Sub FireToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles FireToolStripMenuItem.Click
Me.BackgroundImage = My.Resources.Fire
TrackBar1.BackColor = Color.Yellow
End Sub
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Mar 29, 2010
I am using a button to check which PCs are online which works fine so far. The problem is that the app is blocked for this time I click on the button and perform this action.
[Code]...
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Nov 6, 2011
When I run the following code in the UI thread, it works without issue.
VB.NET private timer as new timer public sub test()timer.enabled = true timer.interval = 1000 timer.start()addhandler timer.tick, addressof timer_tickend sub private sub timer_tick(...) messagebox.show("fff")end sub
But if I run it within a background thread, nothing happens.
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Apr 21, 2011
I have some code in a textbox.Validating event I don't want to execute when the user clicks on the form "X" button to close the form.
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Jul 23, 2009
i know how to toggle a button background color when i click on another button? That means i have two buttons on a window form and when i click on button A, button B will toggle its own background color based on the click event in button A.
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May 8, 2011
I want to change the background color of an element when the mouseEnter event fires. How to make the color of the background darker?? I thought I can use an opacity mask, but it's a gradient, but I need it to be solid. Also it has to be in visual basic code, not in xaml.
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Feb 4, 2011
I have successfully converted the FullCalendar into asp.net / VB and it works perfectly. I am struggling to change the background colour of an event based on a SQL query. I have tried many of the links on StackOverflow and on the Full Calendar Docs [URL] but I have barely any knowledge of jQuery/Javascript so this is proving very difficult for me.I have 5 Employees and I would like each of them to have a unique colour on the Calendar. In my SQL table there is a SalesPersonID field for each employee. I want to change the colour based on the ID. e.g.: (I know this will not work in this scenario, it is purely for info)
If "SalesPersonID" = "1" Then
cevent.className = "Steve"
ElseIf "SalesPersonID" = "2" Then
[code]....
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Apr 18, 2011
The event handlers in my parent class are never called though the events are raised in the child class.
The Code:
Public Class childForm
Public Event checkboxchangedEvent(ByVal checkbox1 As Boolean, ByVal checkbox2 As Boolean)
Private Sub checkboxchanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CheckBox1.CheckedChanged, CheckBox2.CheckedChanged
[code]....
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Jul 15, 2011
I'm writing an application in Visual Basic Express 2008, part of the function being to walk through a folder structure starting from a user specified folder. In my research, I found this thing called a background worker which seemed an appropriate tool to use given the potential size of a target folder structure. I successfully installed the two examples from the library here, and believe I understand the principles involved. Even so, having tried to build this feature into my application, it seems as though it is not working as expected, and, as predicted, debugging a multi-threaded application is a pain in the extremity.
I have this fragment under my "start" button click event -
HomeSource.Enabled = False
HomeCopy.Enabled = False
HomeReport.Enabled = False
[Code].....
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Jul 18, 2010
im thinking just because an app has been sent ton system tray does not mean its a "back ground worker"
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