How to track multiple BackgroundworkerX.Runworkercompleted operations
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I am trying to use a single handler to cover the end of multiple backgroundworker activities and cannot find a way to get the information about the specific backgroundworker using the backgroundworkercompleted event.
My code to catch the event is as below:
Private Sub BGx_RunWorkerCompleted(ByVal sender As Object, ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted, BackgroundWorker2.RunWorkerCompleted, BackgroundWorker3.RunWorkerCompleted, BackgroundWorker4.RunWorkerCompleted, BackgroundWorker5.RunWorkerCompleted, BackgroundWorker6.RunWorkerCompleted, BackgroundWorker7.RunWorkerCompleted, BackgroundWorker8.RunWorkerCompleted
'Do work here based on completed Backgroundworker
For BG = 1 To 8
If Not DSWorkers(BG).IsBusy Then
If DStatus(BG) = -2 Then : DStatus(BG) = -1 : End If
End If
Next
Complete()
End Sub
There is nothing on the "Do Work Here" section because I do not know how to capture and have been unable to find details of the backgroundworkercompleted event id.
Please - any pointers as to how I can identify the specific completed BackgroundWorker
vb.net backgroundworker background-process
add a comment |
up vote
0
down vote
favorite
I am trying to use a single handler to cover the end of multiple backgroundworker activities and cannot find a way to get the information about the specific backgroundworker using the backgroundworkercompleted event.
My code to catch the event is as below:
Private Sub BGx_RunWorkerCompleted(ByVal sender As Object, ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted, BackgroundWorker2.RunWorkerCompleted, BackgroundWorker3.RunWorkerCompleted, BackgroundWorker4.RunWorkerCompleted, BackgroundWorker5.RunWorkerCompleted, BackgroundWorker6.RunWorkerCompleted, BackgroundWorker7.RunWorkerCompleted, BackgroundWorker8.RunWorkerCompleted
'Do work here based on completed Backgroundworker
For BG = 1 To 8
If Not DSWorkers(BG).IsBusy Then
If DStatus(BG) = -2 Then : DStatus(BG) = -1 : End If
End If
Next
Complete()
End Sub
There is nothing on the "Do Work Here" section because I do not know how to capture and have been unable to find details of the backgroundworkercompleted event id.
Please - any pointers as to how I can identify the specific completed BackgroundWorker
vb.net backgroundworker background-process
add a comment |
up vote
0
down vote
favorite
up vote
0
down vote
favorite
I am trying to use a single handler to cover the end of multiple backgroundworker activities and cannot find a way to get the information about the specific backgroundworker using the backgroundworkercompleted event.
My code to catch the event is as below:
Private Sub BGx_RunWorkerCompleted(ByVal sender As Object, ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted, BackgroundWorker2.RunWorkerCompleted, BackgroundWorker3.RunWorkerCompleted, BackgroundWorker4.RunWorkerCompleted, BackgroundWorker5.RunWorkerCompleted, BackgroundWorker6.RunWorkerCompleted, BackgroundWorker7.RunWorkerCompleted, BackgroundWorker8.RunWorkerCompleted
'Do work here based on completed Backgroundworker
For BG = 1 To 8
If Not DSWorkers(BG).IsBusy Then
If DStatus(BG) = -2 Then : DStatus(BG) = -1 : End If
End If
Next
Complete()
End Sub
There is nothing on the "Do Work Here" section because I do not know how to capture and have been unable to find details of the backgroundworkercompleted event id.
Please - any pointers as to how I can identify the specific completed BackgroundWorker
vb.net backgroundworker background-process
I am trying to use a single handler to cover the end of multiple backgroundworker activities and cannot find a way to get the information about the specific backgroundworker using the backgroundworkercompleted event.
My code to catch the event is as below:
Private Sub BGx_RunWorkerCompleted(ByVal sender As Object, ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted, BackgroundWorker2.RunWorkerCompleted, BackgroundWorker3.RunWorkerCompleted, BackgroundWorker4.RunWorkerCompleted, BackgroundWorker5.RunWorkerCompleted, BackgroundWorker6.RunWorkerCompleted, BackgroundWorker7.RunWorkerCompleted, BackgroundWorker8.RunWorkerCompleted
'Do work here based on completed Backgroundworker
For BG = 1 To 8
If Not DSWorkers(BG).IsBusy Then
If DStatus(BG) = -2 Then : DStatus(BG) = -1 : End If
End If
Next
Complete()
End Sub
There is nothing on the "Do Work Here" section because I do not know how to capture and have been unable to find details of the backgroundworkercompleted event id.
Please - any pointers as to how I can identify the specific completed BackgroundWorker
vb.net backgroundworker background-process
vb.net backgroundworker background-process
edited Nov 12 at 4:48
asked Nov 12 at 1:05
Terval
134
134
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
up vote
0
down vote
As with all event handlers, the sender
parameter is a reference to the object that raised the event, so you can access the actual BackgroundWorker
that has completed its work via that. If you need some data other than that, you assign it to the e.Result
property in the DoWork
event handler and get it back from the e.Result
property in the RunWorkerCompleted
event handler. e.Result
works for getting data out of the DoWork
event handler much as e.Argument
works for getting data in.
Check this out for some examples of using BackgroundWorker
objects, including passing data out using e.Result
. You might also like to checkout my own BackgroundMultiWorker
class, which basically combines the functionality of multiple BackgroundWorker
objects into a single BackgroundMultiWorker
object. It identifies each task using a token.
EDIT:
Here's an example that may help with this issue and your task in general:
Imports System.ComponentModel
Imports System.Threading
Public Class Form1
Private ReadOnly resultsByWorker As New Dictionary(Of BackgroundWorker, BackgroundWorkerResult)
Private ReadOnly rng As New Random
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'The NumericUpDown is used to select the index of a BackgroundWorker to cancel.
With NumericUpDown1
.DecimalPlaces = 0
.Minimum = 0
.Maximum = 9
End With
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
'Create 10 BackgroundWorkers and run them.
For i = 1 To 10
Dim worker As New BackgroundWorker
resultsByWorker.Add(worker, New BackgroundWorkerResult)
AddHandler worker.DoWork, AddressOf workers_DoWork
AddHandler worker.RunWorkerCompleted, AddressOf workers_RunWorkerCompleted
worker.WorkerSupportsCancellation = True
worker.RunWorkerAsync()
Next
End Sub
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
Dim index = Convert.ToInt32(NumericUpDown1.Value)
Dim worker = resultsByWorker.Keys.ToArray()(index)
If worker.IsBusy Then
'Cancel the BackgroundWorker at the specified index.
worker.CancelAsync()
End If
End Sub
Private Sub workers_DoWork(sender As Object, e As DoWorkEventArgs)
Dim worker = DirectCast(sender, BackgroundWorker)
'Do work for a random number of seconds between 10 and 20.
Dim period = rng.Next(10, 20 + 1)
For i = 0 To period
If worker.CancellationPending Then
e.Cancel = True
Return
End If
'Simulate work.
Thread.Sleep(1000)
Next
'The work was completed without being cancelled.
e.Result = period
End Sub
Private Sub workers_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs)
Dim worker = DirectCast(sender, BackgroundWorker)
Dim result = resultsByWorker(worker)
If e.Cancelled Then
result.WasCancelled = True
Else
result.Result = CInt(e.Result)
End If
Dim workers = resultsByWorker.Keys.ToArray()
If Not workers.Any(Function(bgw) bgw.IsBusy) Then
'All work has completed so display the results.
Dim results As New List(Of String)
For i = 0 To workers.GetUpperBound(0)
worker = workers(i)
result = resultsByWorker(worker)
results.Add($"Worker {i} {If(result.WasCancelled, "was cancelled", $"completed {result.Result} iterations")}.")
Next
MessageBox.Show(String.Join(Environment.NewLine, results))
End If
End Sub
End Class
Public Class BackgroundWorkerResult
Public Property WasCancelled As Boolean
Public Property Result As Integer
End Class
Here is that example reworked to use a single instance of the BackgroundMultiWorker
is linked to instead of multiple instances of the BackgroundWorker
class.
Imports System.Threading
Public Class Form1
Private WithEvents worker As New BackgroundMultiWorker With {.WorkerSupportsCancellation = True}
Private ReadOnly results(9) As BackgroundWorkerResult
Private ReadOnly rng As New Random
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'The NumericUpDown is used to select the index of a BackgroundWorker to cancel.
With NumericUpDown1
.DecimalPlaces = 0
.Minimum = 0
.Maximum = results.GetUpperBound(0)
End With
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
'Create 10 BackgroundWorkers and run them.
For i = 0 To results.GetUpperBound(0)
results(i) = New BackgroundWorkerResult
worker.RunWorkerAsync(i)
Next
End Sub
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
Dim index = Convert.ToInt32(NumericUpDown1.Value)
If worker.IsBusy(index) Then
'Cancel the BackgroundWorker at the specified index.
worker.CancelAsync(index)
End If
End Sub
Private Sub worker_DoWork(sender As Object, e As DoWorkEventArgs) Handles worker.DoWork
'Do work for a random number of seconds between 10 and 20.
Dim period = rng.Next(10, 20 + 1)
For i = 0 To period
If worker.IsCancellationPending(e.Token) Then
e.Cancel = True
Return
End If
'Simulate work.
Thread.Sleep(1000)
Next
'The work was completed without being cancelled.
e.Result = period
End Sub
Private Sub workers_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs) Handles worker.RunWorkerCompleted
Dim result = results(CInt(e.Token))
If e.Cancelled Then
result.WasCancelled = True
Else
result.Result = CInt(e.Result)
End If
If Not worker.IsBusy() Then
'All work has completed so display the results.
Dim output As New List(Of String)
For i = 0 To results.GetUpperBound(0)
result = results(i)
output.Add($"Task {i} {If(result.WasCancelled, "was cancelled", $"completed {result.Result} iterations")}.")
Next
MessageBox.Show(String.Join(Environment.NewLine, output))
End If
End Sub
End Class
Public Class BackgroundWorkerResult
Public Property WasCancelled As Boolean
Public Property Result As Integer
End Class
Thanks for that - had been trying to use the e.result method but this fails if the backgroundworker was cancelled by the user. This s really the problem since I need to do work for the specific backgroundworker IF it was cancelled by the user. I have added some code to pick up an external tag and check ALL background tasks but it would be easier if there was some id info I could get from the sender parameter .. there might be something but I have not been able to find ot.
– Terval
Nov 12 at 4:45
I reread your comments and I am sure the answer is in the sender parameters but how do I call them?... I will need a pointer on this since I have not found the info through my searches or by reading the syntax docs.
– Terval
Nov 12 at 4:53
Looking at your Multiworker. Sounds hopeful.
– Terval
Nov 12 at 5:15
See my edit for a complete code example. I'll rejig that to use aBackgroundMultiWorker
too.
– jmcilhinney
Nov 12 at 5:42
I have added theBackgroundMultiWorker
example.
– jmcilhinney
Nov 12 at 6:09
add a comment |
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
0
down vote
As with all event handlers, the sender
parameter is a reference to the object that raised the event, so you can access the actual BackgroundWorker
that has completed its work via that. If you need some data other than that, you assign it to the e.Result
property in the DoWork
event handler and get it back from the e.Result
property in the RunWorkerCompleted
event handler. e.Result
works for getting data out of the DoWork
event handler much as e.Argument
works for getting data in.
Check this out for some examples of using BackgroundWorker
objects, including passing data out using e.Result
. You might also like to checkout my own BackgroundMultiWorker
class, which basically combines the functionality of multiple BackgroundWorker
objects into a single BackgroundMultiWorker
object. It identifies each task using a token.
EDIT:
Here's an example that may help with this issue and your task in general:
Imports System.ComponentModel
Imports System.Threading
Public Class Form1
Private ReadOnly resultsByWorker As New Dictionary(Of BackgroundWorker, BackgroundWorkerResult)
Private ReadOnly rng As New Random
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'The NumericUpDown is used to select the index of a BackgroundWorker to cancel.
With NumericUpDown1
.DecimalPlaces = 0
.Minimum = 0
.Maximum = 9
End With
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
'Create 10 BackgroundWorkers and run them.
For i = 1 To 10
Dim worker As New BackgroundWorker
resultsByWorker.Add(worker, New BackgroundWorkerResult)
AddHandler worker.DoWork, AddressOf workers_DoWork
AddHandler worker.RunWorkerCompleted, AddressOf workers_RunWorkerCompleted
worker.WorkerSupportsCancellation = True
worker.RunWorkerAsync()
Next
End Sub
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
Dim index = Convert.ToInt32(NumericUpDown1.Value)
Dim worker = resultsByWorker.Keys.ToArray()(index)
If worker.IsBusy Then
'Cancel the BackgroundWorker at the specified index.
worker.CancelAsync()
End If
End Sub
Private Sub workers_DoWork(sender As Object, e As DoWorkEventArgs)
Dim worker = DirectCast(sender, BackgroundWorker)
'Do work for a random number of seconds between 10 and 20.
Dim period = rng.Next(10, 20 + 1)
For i = 0 To period
If worker.CancellationPending Then
e.Cancel = True
Return
End If
'Simulate work.
Thread.Sleep(1000)
Next
'The work was completed without being cancelled.
e.Result = period
End Sub
Private Sub workers_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs)
Dim worker = DirectCast(sender, BackgroundWorker)
Dim result = resultsByWorker(worker)
If e.Cancelled Then
result.WasCancelled = True
Else
result.Result = CInt(e.Result)
End If
Dim workers = resultsByWorker.Keys.ToArray()
If Not workers.Any(Function(bgw) bgw.IsBusy) Then
'All work has completed so display the results.
Dim results As New List(Of String)
For i = 0 To workers.GetUpperBound(0)
worker = workers(i)
result = resultsByWorker(worker)
results.Add($"Worker {i} {If(result.WasCancelled, "was cancelled", $"completed {result.Result} iterations")}.")
Next
MessageBox.Show(String.Join(Environment.NewLine, results))
End If
End Sub
End Class
Public Class BackgroundWorkerResult
Public Property WasCancelled As Boolean
Public Property Result As Integer
End Class
Here is that example reworked to use a single instance of the BackgroundMultiWorker
is linked to instead of multiple instances of the BackgroundWorker
class.
Imports System.Threading
Public Class Form1
Private WithEvents worker As New BackgroundMultiWorker With {.WorkerSupportsCancellation = True}
Private ReadOnly results(9) As BackgroundWorkerResult
Private ReadOnly rng As New Random
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'The NumericUpDown is used to select the index of a BackgroundWorker to cancel.
With NumericUpDown1
.DecimalPlaces = 0
.Minimum = 0
.Maximum = results.GetUpperBound(0)
End With
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
'Create 10 BackgroundWorkers and run them.
For i = 0 To results.GetUpperBound(0)
results(i) = New BackgroundWorkerResult
worker.RunWorkerAsync(i)
Next
End Sub
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
Dim index = Convert.ToInt32(NumericUpDown1.Value)
If worker.IsBusy(index) Then
'Cancel the BackgroundWorker at the specified index.
worker.CancelAsync(index)
End If
End Sub
Private Sub worker_DoWork(sender As Object, e As DoWorkEventArgs) Handles worker.DoWork
'Do work for a random number of seconds between 10 and 20.
Dim period = rng.Next(10, 20 + 1)
For i = 0 To period
If worker.IsCancellationPending(e.Token) Then
e.Cancel = True
Return
End If
'Simulate work.
Thread.Sleep(1000)
Next
'The work was completed without being cancelled.
e.Result = period
End Sub
Private Sub workers_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs) Handles worker.RunWorkerCompleted
Dim result = results(CInt(e.Token))
If e.Cancelled Then
result.WasCancelled = True
Else
result.Result = CInt(e.Result)
End If
If Not worker.IsBusy() Then
'All work has completed so display the results.
Dim output As New List(Of String)
For i = 0 To results.GetUpperBound(0)
result = results(i)
output.Add($"Task {i} {If(result.WasCancelled, "was cancelled", $"completed {result.Result} iterations")}.")
Next
MessageBox.Show(String.Join(Environment.NewLine, output))
End If
End Sub
End Class
Public Class BackgroundWorkerResult
Public Property WasCancelled As Boolean
Public Property Result As Integer
End Class
Thanks for that - had been trying to use the e.result method but this fails if the backgroundworker was cancelled by the user. This s really the problem since I need to do work for the specific backgroundworker IF it was cancelled by the user. I have added some code to pick up an external tag and check ALL background tasks but it would be easier if there was some id info I could get from the sender parameter .. there might be something but I have not been able to find ot.
– Terval
Nov 12 at 4:45
I reread your comments and I am sure the answer is in the sender parameters but how do I call them?... I will need a pointer on this since I have not found the info through my searches or by reading the syntax docs.
– Terval
Nov 12 at 4:53
Looking at your Multiworker. Sounds hopeful.
– Terval
Nov 12 at 5:15
See my edit for a complete code example. I'll rejig that to use aBackgroundMultiWorker
too.
– jmcilhinney
Nov 12 at 5:42
I have added theBackgroundMultiWorker
example.
– jmcilhinney
Nov 12 at 6:09
add a comment |
up vote
0
down vote
As with all event handlers, the sender
parameter is a reference to the object that raised the event, so you can access the actual BackgroundWorker
that has completed its work via that. If you need some data other than that, you assign it to the e.Result
property in the DoWork
event handler and get it back from the e.Result
property in the RunWorkerCompleted
event handler. e.Result
works for getting data out of the DoWork
event handler much as e.Argument
works for getting data in.
Check this out for some examples of using BackgroundWorker
objects, including passing data out using e.Result
. You might also like to checkout my own BackgroundMultiWorker
class, which basically combines the functionality of multiple BackgroundWorker
objects into a single BackgroundMultiWorker
object. It identifies each task using a token.
EDIT:
Here's an example that may help with this issue and your task in general:
Imports System.ComponentModel
Imports System.Threading
Public Class Form1
Private ReadOnly resultsByWorker As New Dictionary(Of BackgroundWorker, BackgroundWorkerResult)
Private ReadOnly rng As New Random
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'The NumericUpDown is used to select the index of a BackgroundWorker to cancel.
With NumericUpDown1
.DecimalPlaces = 0
.Minimum = 0
.Maximum = 9
End With
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
'Create 10 BackgroundWorkers and run them.
For i = 1 To 10
Dim worker As New BackgroundWorker
resultsByWorker.Add(worker, New BackgroundWorkerResult)
AddHandler worker.DoWork, AddressOf workers_DoWork
AddHandler worker.RunWorkerCompleted, AddressOf workers_RunWorkerCompleted
worker.WorkerSupportsCancellation = True
worker.RunWorkerAsync()
Next
End Sub
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
Dim index = Convert.ToInt32(NumericUpDown1.Value)
Dim worker = resultsByWorker.Keys.ToArray()(index)
If worker.IsBusy Then
'Cancel the BackgroundWorker at the specified index.
worker.CancelAsync()
End If
End Sub
Private Sub workers_DoWork(sender As Object, e As DoWorkEventArgs)
Dim worker = DirectCast(sender, BackgroundWorker)
'Do work for a random number of seconds between 10 and 20.
Dim period = rng.Next(10, 20 + 1)
For i = 0 To period
If worker.CancellationPending Then
e.Cancel = True
Return
End If
'Simulate work.
Thread.Sleep(1000)
Next
'The work was completed without being cancelled.
e.Result = period
End Sub
Private Sub workers_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs)
Dim worker = DirectCast(sender, BackgroundWorker)
Dim result = resultsByWorker(worker)
If e.Cancelled Then
result.WasCancelled = True
Else
result.Result = CInt(e.Result)
End If
Dim workers = resultsByWorker.Keys.ToArray()
If Not workers.Any(Function(bgw) bgw.IsBusy) Then
'All work has completed so display the results.
Dim results As New List(Of String)
For i = 0 To workers.GetUpperBound(0)
worker = workers(i)
result = resultsByWorker(worker)
results.Add($"Worker {i} {If(result.WasCancelled, "was cancelled", $"completed {result.Result} iterations")}.")
Next
MessageBox.Show(String.Join(Environment.NewLine, results))
End If
End Sub
End Class
Public Class BackgroundWorkerResult
Public Property WasCancelled As Boolean
Public Property Result As Integer
End Class
Here is that example reworked to use a single instance of the BackgroundMultiWorker
is linked to instead of multiple instances of the BackgroundWorker
class.
Imports System.Threading
Public Class Form1
Private WithEvents worker As New BackgroundMultiWorker With {.WorkerSupportsCancellation = True}
Private ReadOnly results(9) As BackgroundWorkerResult
Private ReadOnly rng As New Random
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'The NumericUpDown is used to select the index of a BackgroundWorker to cancel.
With NumericUpDown1
.DecimalPlaces = 0
.Minimum = 0
.Maximum = results.GetUpperBound(0)
End With
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
'Create 10 BackgroundWorkers and run them.
For i = 0 To results.GetUpperBound(0)
results(i) = New BackgroundWorkerResult
worker.RunWorkerAsync(i)
Next
End Sub
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
Dim index = Convert.ToInt32(NumericUpDown1.Value)
If worker.IsBusy(index) Then
'Cancel the BackgroundWorker at the specified index.
worker.CancelAsync(index)
End If
End Sub
Private Sub worker_DoWork(sender As Object, e As DoWorkEventArgs) Handles worker.DoWork
'Do work for a random number of seconds between 10 and 20.
Dim period = rng.Next(10, 20 + 1)
For i = 0 To period
If worker.IsCancellationPending(e.Token) Then
e.Cancel = True
Return
End If
'Simulate work.
Thread.Sleep(1000)
Next
'The work was completed without being cancelled.
e.Result = period
End Sub
Private Sub workers_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs) Handles worker.RunWorkerCompleted
Dim result = results(CInt(e.Token))
If e.Cancelled Then
result.WasCancelled = True
Else
result.Result = CInt(e.Result)
End If
If Not worker.IsBusy() Then
'All work has completed so display the results.
Dim output As New List(Of String)
For i = 0 To results.GetUpperBound(0)
result = results(i)
output.Add($"Task {i} {If(result.WasCancelled, "was cancelled", $"completed {result.Result} iterations")}.")
Next
MessageBox.Show(String.Join(Environment.NewLine, output))
End If
End Sub
End Class
Public Class BackgroundWorkerResult
Public Property WasCancelled As Boolean
Public Property Result As Integer
End Class
Thanks for that - had been trying to use the e.result method but this fails if the backgroundworker was cancelled by the user. This s really the problem since I need to do work for the specific backgroundworker IF it was cancelled by the user. I have added some code to pick up an external tag and check ALL background tasks but it would be easier if there was some id info I could get from the sender parameter .. there might be something but I have not been able to find ot.
– Terval
Nov 12 at 4:45
I reread your comments and I am sure the answer is in the sender parameters but how do I call them?... I will need a pointer on this since I have not found the info through my searches or by reading the syntax docs.
– Terval
Nov 12 at 4:53
Looking at your Multiworker. Sounds hopeful.
– Terval
Nov 12 at 5:15
See my edit for a complete code example. I'll rejig that to use aBackgroundMultiWorker
too.
– jmcilhinney
Nov 12 at 5:42
I have added theBackgroundMultiWorker
example.
– jmcilhinney
Nov 12 at 6:09
add a comment |
up vote
0
down vote
up vote
0
down vote
As with all event handlers, the sender
parameter is a reference to the object that raised the event, so you can access the actual BackgroundWorker
that has completed its work via that. If you need some data other than that, you assign it to the e.Result
property in the DoWork
event handler and get it back from the e.Result
property in the RunWorkerCompleted
event handler. e.Result
works for getting data out of the DoWork
event handler much as e.Argument
works for getting data in.
Check this out for some examples of using BackgroundWorker
objects, including passing data out using e.Result
. You might also like to checkout my own BackgroundMultiWorker
class, which basically combines the functionality of multiple BackgroundWorker
objects into a single BackgroundMultiWorker
object. It identifies each task using a token.
EDIT:
Here's an example that may help with this issue and your task in general:
Imports System.ComponentModel
Imports System.Threading
Public Class Form1
Private ReadOnly resultsByWorker As New Dictionary(Of BackgroundWorker, BackgroundWorkerResult)
Private ReadOnly rng As New Random
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'The NumericUpDown is used to select the index of a BackgroundWorker to cancel.
With NumericUpDown1
.DecimalPlaces = 0
.Minimum = 0
.Maximum = 9
End With
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
'Create 10 BackgroundWorkers and run them.
For i = 1 To 10
Dim worker As New BackgroundWorker
resultsByWorker.Add(worker, New BackgroundWorkerResult)
AddHandler worker.DoWork, AddressOf workers_DoWork
AddHandler worker.RunWorkerCompleted, AddressOf workers_RunWorkerCompleted
worker.WorkerSupportsCancellation = True
worker.RunWorkerAsync()
Next
End Sub
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
Dim index = Convert.ToInt32(NumericUpDown1.Value)
Dim worker = resultsByWorker.Keys.ToArray()(index)
If worker.IsBusy Then
'Cancel the BackgroundWorker at the specified index.
worker.CancelAsync()
End If
End Sub
Private Sub workers_DoWork(sender As Object, e As DoWorkEventArgs)
Dim worker = DirectCast(sender, BackgroundWorker)
'Do work for a random number of seconds between 10 and 20.
Dim period = rng.Next(10, 20 + 1)
For i = 0 To period
If worker.CancellationPending Then
e.Cancel = True
Return
End If
'Simulate work.
Thread.Sleep(1000)
Next
'The work was completed without being cancelled.
e.Result = period
End Sub
Private Sub workers_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs)
Dim worker = DirectCast(sender, BackgroundWorker)
Dim result = resultsByWorker(worker)
If e.Cancelled Then
result.WasCancelled = True
Else
result.Result = CInt(e.Result)
End If
Dim workers = resultsByWorker.Keys.ToArray()
If Not workers.Any(Function(bgw) bgw.IsBusy) Then
'All work has completed so display the results.
Dim results As New List(Of String)
For i = 0 To workers.GetUpperBound(0)
worker = workers(i)
result = resultsByWorker(worker)
results.Add($"Worker {i} {If(result.WasCancelled, "was cancelled", $"completed {result.Result} iterations")}.")
Next
MessageBox.Show(String.Join(Environment.NewLine, results))
End If
End Sub
End Class
Public Class BackgroundWorkerResult
Public Property WasCancelled As Boolean
Public Property Result As Integer
End Class
Here is that example reworked to use a single instance of the BackgroundMultiWorker
is linked to instead of multiple instances of the BackgroundWorker
class.
Imports System.Threading
Public Class Form1
Private WithEvents worker As New BackgroundMultiWorker With {.WorkerSupportsCancellation = True}
Private ReadOnly results(9) As BackgroundWorkerResult
Private ReadOnly rng As New Random
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'The NumericUpDown is used to select the index of a BackgroundWorker to cancel.
With NumericUpDown1
.DecimalPlaces = 0
.Minimum = 0
.Maximum = results.GetUpperBound(0)
End With
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
'Create 10 BackgroundWorkers and run them.
For i = 0 To results.GetUpperBound(0)
results(i) = New BackgroundWorkerResult
worker.RunWorkerAsync(i)
Next
End Sub
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
Dim index = Convert.ToInt32(NumericUpDown1.Value)
If worker.IsBusy(index) Then
'Cancel the BackgroundWorker at the specified index.
worker.CancelAsync(index)
End If
End Sub
Private Sub worker_DoWork(sender As Object, e As DoWorkEventArgs) Handles worker.DoWork
'Do work for a random number of seconds between 10 and 20.
Dim period = rng.Next(10, 20 + 1)
For i = 0 To period
If worker.IsCancellationPending(e.Token) Then
e.Cancel = True
Return
End If
'Simulate work.
Thread.Sleep(1000)
Next
'The work was completed without being cancelled.
e.Result = period
End Sub
Private Sub workers_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs) Handles worker.RunWorkerCompleted
Dim result = results(CInt(e.Token))
If e.Cancelled Then
result.WasCancelled = True
Else
result.Result = CInt(e.Result)
End If
If Not worker.IsBusy() Then
'All work has completed so display the results.
Dim output As New List(Of String)
For i = 0 To results.GetUpperBound(0)
result = results(i)
output.Add($"Task {i} {If(result.WasCancelled, "was cancelled", $"completed {result.Result} iterations")}.")
Next
MessageBox.Show(String.Join(Environment.NewLine, output))
End If
End Sub
End Class
Public Class BackgroundWorkerResult
Public Property WasCancelled As Boolean
Public Property Result As Integer
End Class
As with all event handlers, the sender
parameter is a reference to the object that raised the event, so you can access the actual BackgroundWorker
that has completed its work via that. If you need some data other than that, you assign it to the e.Result
property in the DoWork
event handler and get it back from the e.Result
property in the RunWorkerCompleted
event handler. e.Result
works for getting data out of the DoWork
event handler much as e.Argument
works for getting data in.
Check this out for some examples of using BackgroundWorker
objects, including passing data out using e.Result
. You might also like to checkout my own BackgroundMultiWorker
class, which basically combines the functionality of multiple BackgroundWorker
objects into a single BackgroundMultiWorker
object. It identifies each task using a token.
EDIT:
Here's an example that may help with this issue and your task in general:
Imports System.ComponentModel
Imports System.Threading
Public Class Form1
Private ReadOnly resultsByWorker As New Dictionary(Of BackgroundWorker, BackgroundWorkerResult)
Private ReadOnly rng As New Random
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'The NumericUpDown is used to select the index of a BackgroundWorker to cancel.
With NumericUpDown1
.DecimalPlaces = 0
.Minimum = 0
.Maximum = 9
End With
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
'Create 10 BackgroundWorkers and run them.
For i = 1 To 10
Dim worker As New BackgroundWorker
resultsByWorker.Add(worker, New BackgroundWorkerResult)
AddHandler worker.DoWork, AddressOf workers_DoWork
AddHandler worker.RunWorkerCompleted, AddressOf workers_RunWorkerCompleted
worker.WorkerSupportsCancellation = True
worker.RunWorkerAsync()
Next
End Sub
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
Dim index = Convert.ToInt32(NumericUpDown1.Value)
Dim worker = resultsByWorker.Keys.ToArray()(index)
If worker.IsBusy Then
'Cancel the BackgroundWorker at the specified index.
worker.CancelAsync()
End If
End Sub
Private Sub workers_DoWork(sender As Object, e As DoWorkEventArgs)
Dim worker = DirectCast(sender, BackgroundWorker)
'Do work for a random number of seconds between 10 and 20.
Dim period = rng.Next(10, 20 + 1)
For i = 0 To period
If worker.CancellationPending Then
e.Cancel = True
Return
End If
'Simulate work.
Thread.Sleep(1000)
Next
'The work was completed without being cancelled.
e.Result = period
End Sub
Private Sub workers_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs)
Dim worker = DirectCast(sender, BackgroundWorker)
Dim result = resultsByWorker(worker)
If e.Cancelled Then
result.WasCancelled = True
Else
result.Result = CInt(e.Result)
End If
Dim workers = resultsByWorker.Keys.ToArray()
If Not workers.Any(Function(bgw) bgw.IsBusy) Then
'All work has completed so display the results.
Dim results As New List(Of String)
For i = 0 To workers.GetUpperBound(0)
worker = workers(i)
result = resultsByWorker(worker)
results.Add($"Worker {i} {If(result.WasCancelled, "was cancelled", $"completed {result.Result} iterations")}.")
Next
MessageBox.Show(String.Join(Environment.NewLine, results))
End If
End Sub
End Class
Public Class BackgroundWorkerResult
Public Property WasCancelled As Boolean
Public Property Result As Integer
End Class
Here is that example reworked to use a single instance of the BackgroundMultiWorker
is linked to instead of multiple instances of the BackgroundWorker
class.
Imports System.Threading
Public Class Form1
Private WithEvents worker As New BackgroundMultiWorker With {.WorkerSupportsCancellation = True}
Private ReadOnly results(9) As BackgroundWorkerResult
Private ReadOnly rng As New Random
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'The NumericUpDown is used to select the index of a BackgroundWorker to cancel.
With NumericUpDown1
.DecimalPlaces = 0
.Minimum = 0
.Maximum = results.GetUpperBound(0)
End With
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
'Create 10 BackgroundWorkers and run them.
For i = 0 To results.GetUpperBound(0)
results(i) = New BackgroundWorkerResult
worker.RunWorkerAsync(i)
Next
End Sub
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
Dim index = Convert.ToInt32(NumericUpDown1.Value)
If worker.IsBusy(index) Then
'Cancel the BackgroundWorker at the specified index.
worker.CancelAsync(index)
End If
End Sub
Private Sub worker_DoWork(sender As Object, e As DoWorkEventArgs) Handles worker.DoWork
'Do work for a random number of seconds between 10 and 20.
Dim period = rng.Next(10, 20 + 1)
For i = 0 To period
If worker.IsCancellationPending(e.Token) Then
e.Cancel = True
Return
End If
'Simulate work.
Thread.Sleep(1000)
Next
'The work was completed without being cancelled.
e.Result = period
End Sub
Private Sub workers_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs) Handles worker.RunWorkerCompleted
Dim result = results(CInt(e.Token))
If e.Cancelled Then
result.WasCancelled = True
Else
result.Result = CInt(e.Result)
End If
If Not worker.IsBusy() Then
'All work has completed so display the results.
Dim output As New List(Of String)
For i = 0 To results.GetUpperBound(0)
result = results(i)
output.Add($"Task {i} {If(result.WasCancelled, "was cancelled", $"completed {result.Result} iterations")}.")
Next
MessageBox.Show(String.Join(Environment.NewLine, output))
End If
End Sub
End Class
Public Class BackgroundWorkerResult
Public Property WasCancelled As Boolean
Public Property Result As Integer
End Class
edited Nov 12 at 6:08
answered Nov 12 at 1:34
jmcilhinney
25k21932
25k21932
Thanks for that - had been trying to use the e.result method but this fails if the backgroundworker was cancelled by the user. This s really the problem since I need to do work for the specific backgroundworker IF it was cancelled by the user. I have added some code to pick up an external tag and check ALL background tasks but it would be easier if there was some id info I could get from the sender parameter .. there might be something but I have not been able to find ot.
– Terval
Nov 12 at 4:45
I reread your comments and I am sure the answer is in the sender parameters but how do I call them?... I will need a pointer on this since I have not found the info through my searches or by reading the syntax docs.
– Terval
Nov 12 at 4:53
Looking at your Multiworker. Sounds hopeful.
– Terval
Nov 12 at 5:15
See my edit for a complete code example. I'll rejig that to use aBackgroundMultiWorker
too.
– jmcilhinney
Nov 12 at 5:42
I have added theBackgroundMultiWorker
example.
– jmcilhinney
Nov 12 at 6:09
add a comment |
Thanks for that - had been trying to use the e.result method but this fails if the backgroundworker was cancelled by the user. This s really the problem since I need to do work for the specific backgroundworker IF it was cancelled by the user. I have added some code to pick up an external tag and check ALL background tasks but it would be easier if there was some id info I could get from the sender parameter .. there might be something but I have not been able to find ot.
– Terval
Nov 12 at 4:45
I reread your comments and I am sure the answer is in the sender parameters but how do I call them?... I will need a pointer on this since I have not found the info through my searches or by reading the syntax docs.
– Terval
Nov 12 at 4:53
Looking at your Multiworker. Sounds hopeful.
– Terval
Nov 12 at 5:15
See my edit for a complete code example. I'll rejig that to use aBackgroundMultiWorker
too.
– jmcilhinney
Nov 12 at 5:42
I have added theBackgroundMultiWorker
example.
– jmcilhinney
Nov 12 at 6:09
Thanks for that - had been trying to use the e.result method but this fails if the backgroundworker was cancelled by the user. This s really the problem since I need to do work for the specific backgroundworker IF it was cancelled by the user. I have added some code to pick up an external tag and check ALL background tasks but it would be easier if there was some id info I could get from the sender parameter .. there might be something but I have not been able to find ot.
– Terval
Nov 12 at 4:45
Thanks for that - had been trying to use the e.result method but this fails if the backgroundworker was cancelled by the user. This s really the problem since I need to do work for the specific backgroundworker IF it was cancelled by the user. I have added some code to pick up an external tag and check ALL background tasks but it would be easier if there was some id info I could get from the sender parameter .. there might be something but I have not been able to find ot.
– Terval
Nov 12 at 4:45
I reread your comments and I am sure the answer is in the sender parameters but how do I call them?... I will need a pointer on this since I have not found the info through my searches or by reading the syntax docs.
– Terval
Nov 12 at 4:53
I reread your comments and I am sure the answer is in the sender parameters but how do I call them?... I will need a pointer on this since I have not found the info through my searches or by reading the syntax docs.
– Terval
Nov 12 at 4:53
Looking at your Multiworker. Sounds hopeful.
– Terval
Nov 12 at 5:15
Looking at your Multiworker. Sounds hopeful.
– Terval
Nov 12 at 5:15
See my edit for a complete code example. I'll rejig that to use a
BackgroundMultiWorker
too.– jmcilhinney
Nov 12 at 5:42
See my edit for a complete code example. I'll rejig that to use a
BackgroundMultiWorker
too.– jmcilhinney
Nov 12 at 5:42
I have added the
BackgroundMultiWorker
example.– jmcilhinney
Nov 12 at 6:09
I have added the
BackgroundMultiWorker
example.– jmcilhinney
Nov 12 at 6:09
add a comment |
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