I am trying to write an app that in the thread will do some tasks, the form lokks like this:and what it should is something like this:
- retrieve data, populate a row in the listview, increase the first progress bar
- retrieve data, populate a row in the listview, increase the first progress bar
- retrieve data, populate a row in the listview, increase the first progress bar
[code]....
My program crashes with the following error:Controls created on one thread cannot be parented to a control on a different thread.Purpose of the program is to add a control from a thread outside the main thread.Below is the code Private Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
[Code]...
I have a program that runs for some time and I would like to update the user on its progress. The rest of the GUI is updated using Delegates and Invokes and such (Java is Soooo much cleaner in this regard - everything is thread safe!!), but there is no invoke method for the progress bar. How can I use a delegate to update the progress bar when there is no invoke to invoke!!
View 1 RepliesI've got a couple of these NumericUpDown controls I put on a form. Without describing too much about the form I basically want to update some variables each time one of these NumUD controls changes value. So for each NumUD I have a call to a Recalculate subroutine within their "changedValue" event.
There are actually two problems. First, if I initialize the "Value" property to something other than zero in VB2010 at DESIGN TIME it won't even open the form when I hit RUN. It gives me a "No Source Available. No symbols loaded for any call stack frame" error. The error box says "InvalidOperationException" was not handled. So if I try to set the initial value of the Value property to anything but zero of either I get this error.
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I've got a bunch of labels that I update regularly in the program, resulting in lagg, which is bad, so how can I update the labels in a thread?
When I try
Thread = New System.Threading.Thread(AddressOf ShowInfo)
Thread.Start()
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1) Which one works better? BackgroundWorker or Multithreading?I have to do lots of processing in my application, I'm not too sure how the two of them works.
2) Can I assign controls in a GroupBox to a thread?Let's say I have to login to a certain forum twice with different accounts, so in GroupBox1 (thread1), I'll be logged in with username "asd", in GroupBox2 (thread2), I'll be logged in with username "zxc", and I have to do lots of processing (mostly html parsing) from there. Is this possible without stressing on memory usage? I'd like to keep my program memory usage under 10k.
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Here is my setup:
Form1.vb - contains RichTextBox1 and BackgroundWorker1, which calls a the Control module.
Control.vb - calls Display module.
Display.vb - calls Form1.SetTextBoxText("text here").[code]...
My observations: When the Display module calls SetTextBoxText, InvokedRequired's is false. Also, if the BackgroundWorker1 (which is in Form1.vb) calls SetTextBoxText, it works. But if BackgroundWorker1 calls a module that calls SetTextBoxText, it doesn't work.
I'm trying to dynamically add a control to a form from an event that is raised from an asynchronious socket's thread.
In other words, when I get an OnDataArrival event is raised from the socket thread, I raise DataArrival event in my form. The form's DataArrival sub then tries to create and parent a control.
Whenever I try this, I get the following error: Controls created in one thread cannot be parented to a control in a different thread.I know a bit about delegates and invoking, and I think that's how to solve this problem, but I don't know where to declare the delegates and how to use them.
Ideally, I want a delegate/invoker to handle the DataArrival sub in the socket class so that everything that happens after that will be thread safe. Can this be done?
Im working on a program ( vb 2005 CE framework ). I have mainly two threads, the main one and another one I use it for a different thing.When I tried to update the UI this exception was thrown : Control.Invoke must be used to interact with controls created on a separate thread.well !I have tried to use the INVOKE, but it wouldn't work. this is where I get the error :
Public Sub PaintKeys()
Dim tempLevel As clsLevel
Dim tempKey As ClsKey
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In main thread I create panel(s) (based on some configuration), and then in the next step based on the file type (like video, ppt, image...) I create appropriate controls (dynamically) to show on the forms.
The creation of the control will be done in separate threads (for each file). After creating the control, it throws an error when I try to add that control to the panel (which was created in the main thread), something like cross thread violation, control was accessed from one thread other that it was created.
Can some one please help me in this regard? In this scenario, everything - creating the panels and controls - will be dynamic. Nothing will be static.I tried some of the articles found here on StackOverflow (like, control.BeginInvoke() .. etc), but wasn't able to solve my problem.
how to access the main ui's labels from a delegate method?
View 7 RepliesThe usual VB way to handle a computationally heavy task is to put it in a background worker thread, while the main thread keeps handling the UI.Say for whatever reason I needed to do this the other way around: the main thread doing the grunt work and the background one updating the UI.Here's what I have so far. The only problem is, while the UI window (Form1) does get redrawn, you can't interact with it, not even move or resize it (the mouse cursor turns to hourglass and won't click).
Public Class ProgressDisplay
Private trd As Thread
Public Sub New()
trd = New Thread(AddressOf threadtask)
[code]....
The client will call it like this (actually in unmanaged c++ over COM but you get the picture):
Dim prog = new ProgressDisplay()
DoLotsOfWork(addressof prog.update) ' DoLotsOfWork method takes a callback argument to keep client informed of progress
below is a small part of my asynchronous TCP connection code. When I connect I'm passing a ListViewItem as Object parameter. I'd like to update the ListViewItem once the connection has been established or an error occurs. ServerConnect runs on a separate thread, because it's an asynchronous connection, so I can't update the ListViewItem directly.
Does anybody know how to update the ListViewItem?
I looked at jmcilhinney's asynchronous TCP example in the Codebank forum, but it confused me. I don't know which parts I need and which parts I don't need.
::edit::
One more thing. I also need to update the ListViewItem in the Read sub, but I'm passing "buffer" as Object, so how would I update the ListViewItem there?
vb.net
Imports System.Net.Sockets
Public Class TCP
Private Socket As TcpClient
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I'm writing a little online game for sport, but my head's gonna explode as I can't figure out why I can't access my forms controls from my clients DoRead() thread.In this procedure I can still obviously access the controls normally.[code]Tried using delegates and invoking, and setting SearchForIllegalCrossThreads false.
View 7 RepliesI am trying to access a dynamically generated Control from a separate thread. But I am always getting a "Stack Overflow Exception" with my code. I am using following code:
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Basic function - enter 5-10 urls. Download all web pages using multi threads and then process it. Then in the end, the text from all threads should end up in a richtextbox. It can't be done using any of my googly searches so i thought about asking this :
how would you update text in a richtextbox from a different thread?
I am being able to download and process web pages. But can't add it to richtextbox.
I have a TCP server app that starts 2 threads when the server is activated, I want the threads to add text to the textbox on the main form. Here's is what I have tried [code]I have added MsgBoxes at points so I know the Sub updatetext_ is being called, and the text is being passed, they are also showing that InvokeRequired is always FALSE. In any case the textbox txtMessages is not being updated.
View 11 RepliesI've looked at the on line doc over and over, and I can't seem to figure out why this won't work. This code runs the thread, and the thread seems to execute the code in the 'threadsafe' sub, however neither the progress bar is updated or the button click performed.
Imports System.Threading
Public Class VisNotify
Inherits Form
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I'm not sure exactly how to describe this. In VB6, there was a Timer command. I could create a variable of type Timer and loop until the current value for Timer exceeded the initial plus a given amount of time. This allowed me to update form variables while the timing loop was executing. How can I do something similar in .NET?[code]...
View 5 RepliesI am new to multi-threading in VB.NET and have come across a problem whereby I am wanting to append text to a text box on a form from a service thread running in the background.
The application I am developing is a client/server listener, I have been able to get the client and server PC's to talk with each other (confirmed through MsgBox), however I am now struggling to get the service thread on the server to append the text to the textbox, nothing vissible occurs.
I have a form named testDebug which calls a class (RemoteSupport), this class does all the handshake tasks and updates the textbox with the connection data.[code]...
The code below works fine when I put it in form1.vb and change "form1" to "me" but I can't seem go get it to work from my class.
VB
Imports System.Threading
Public Class Class1
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I'm writing a program in which I'll receive data using serial port using Comport.DataReceived event which I've written in seperate class. Once I receive data from my comport I need to display that data in my listbox in the form. What is the best way to do this?? I don have much knowledge on using delegates. An
View 14 RepliesI have a form that looks like this:and i'm using a backgroundworker to update the components:
Code:
Private Sub btnGO_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnGO.Click
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[URL]
In my program, I created a list of a class that contains 5 picture boxes, a button, a label, an identifier, and some other stuff. I've got roughly 65 of these in this list. I'd be stupid to hard code all that in. The identifier is a 2nd way of identifying which specific location I'm working on.
Anways, all this is created at compile time. Works perfectly fine.
I then manually start a background worker that pings a collection of components. Based off the success of those pings, the picture boxes are enabled or disabled. Basically a proactive way to see if a collection of devices over multiple locations are actually working.
It's the background worker that fails because of thread-safe calls.
Private Sub bgwStatus_DoWork(ByVal sender As Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles bgwStatus.DoWork
Dim status As Integer
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I have a web app which displays a list of emails that need to be sent for the day. The user can select what emails to send, then click a button to generate them. When they click the Send button, a process gets started on another thread which generates the emails, then cleans up after itself by deleting a temp folder. Once the process is finished, the Repeater is rebound to update the User's view and remove the emails that have just been sent so they don't get sent again.
My problem is that when I delete the temp folder from my 2nd thread, the UI doesn't update with the new Repeater data. It updates correctly if I just delete the files in the folder instead of the folder itself, and it also updates correctly if I run the delete the folder on the original thread instead of the 2nd one.
New Thread code
Dim t as Thread = New Thread(New ThreadStart(AddressOf EmailLetters))
t.Start()
Delete folder code
Dim fs = Server.CreateObject("Scripting.FileSystemObject")
fs.DeleteFolder(Server.MapPath(".") + " mpEmailFiles")
Why won't the UI update to show the new repeater values when I delete a folder on another thread?
When you click the button, a thread gets started and a javascript load script starts executing which does a PostBack every 10 seconds. Each postback checks if the thread is complete and updates the Status label showing the result. If I delete a folder from within the background thread, the final update to the status label never occurs. If I remove the DeleteFolder call, it does.
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<%@ Import Namespace="System.Threading" %>
<%@ Page Language="VB" Debug="true" %>
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I created a new thread to run with a loop to update a textbox (this is just a demo, in reality this thing would go out to a db every x minutes to request an update). I did this on a timer, but i wanted to try to do it on a different thread.. anyways, this is what I have: (one form, one textbox, and this code...)[code]I'm getting a warning through (the "Thread.CurrentThread.Sleep(2000) part is underlined) which states:"Access of Shared Member, Constent Member, enum Member, or Nested Type through an instance; qualifying expression will not be evaluated".
View 5 RepliesI've been searching around for ages now but can't seem to find what I'm looking for, anyway came accross this wonderful place so thought ay I'm creating a rewards system for school where pupil earn points for good behavior which they can then use to purchase things like a packet of pens. (They can also have points deducted for bad behavior)
View 2 RepliesI have a textbox which will accept a user input for a email address or phone number.I want to using a new thread do a search for various results and populate a listbox.I know i need to do this in another thread so my main form will still operate but how can I do this? I've never used threads before and I know it's tricky to get the values from a textbox and also update a list box on another thread.
View 16 RepliesI have an application which runs two threads.
- One thread is the main thread while the other one is to monitor the main thread.
- The errors are written to a custom event log
- There is an event handler to handle the event logs
- When an event occurs I want to create a new thread and update the event to a sql table (pseudo code)
- Also in case their are number of errors/events
how should I handle them (pseudo code)
I'm having trouble getting a progress bar to update. I'd be okay just with a moving marquee bar. Basically, I'm reading a database routine in a SqliteReader.vb class. I need to use the worker_DoWork routine, but I'm not sure how to expose my variables coming from Form1: graphData, graphComputations, m_debug to the worker_DoWork sub. How is this usually done? [Code]
View 3 Replies