VB.net stopping a backgroundworker - vb.net

Question

I want to create a button that could stop my background worker and end all the process it is working on.
Here is my sample backgroundworker code:
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Try
If BackgroundWorker1.IsBusy <> True Then
BackgroundWorker1.RunWorkerAsync()
End If
Catch ex As Exception
End Try
End Sub
Private Sub BackgroundWorker1_DoWork(sender As System.Object, e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
Dim counter As Integer = 1
Do
'updated code with stop function----------------
BackgroundWorker1.WorkerSupportsCancellation = True
If BackgroundWorker1.CancellationPending Then
e.Cancel = True
ProgressBar1.Value = 0
Exit Do
End If
'updated code with stop function----------------
ListBox1.Items.Add(counter)
ProgressBar1.Value = ((counter - 1) / limit) * 100
counter = counter + 1
Loop While(counter <= 999999999999999999)
End Sub
Private Sub BackgroundWorker1_ProgressChanged(sender As System.Object, e As System.ComponentModel.ProgressChangedEventArgs) Handles BackgroundWorker1.ProgressChanged
Try
Catch ex As Exception
End Try
End Sub
Private Sub BackgroundWorker1_Completed(sender As System.Object, e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
Try
Catch ex As Exception
End Try
End Sub
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
System.Windows.Forms.Control.CheckForIllegalCrossThreadCalls = False
End Sub
'updated code with stop function----------------
Private Sub StopButton_Click(sender As Object, e As EventArgs) Handles StopButton.Click
If BackgroundWorker1.IsBusy Then
If BackgroundWorker1.WorkerSupportsCancellation Then
BackgroundWorker1.CancelAsync()
End If
End If
End Sub
'updated code with stop function----------------
I want to reset the loop and return the Progress Bar to 0% when i stop the backgroundworker.
Is this possible?
The code above has been updated and it is now working fine.
I have added this code inside my do loop:
BackgroundWorker1.WorkerSupportsCancellation = True
If BackgroundWorker1.CancellationPending Then
e.Cancel = True
ProgressBar1.Value = 0
Exit Do
End If
I created a button that stops the worker:
Private Sub StopButton_Click(sender As Object, e As EventArgs) Handles StopButton.Click
If BackgroundWorker1.IsBusy Then
If BackgroundWorker1.WorkerSupportsCancellation Then
BackgroundWorker1.CancelAsync()
End If
End If
End Sub

Answer 1

The Backgroundworker class has the method CancelAsync() which you need to call to cancel the execution of the bgw.
You need to set the Backgroundworker.WorkerSupportsCancellation property to true and inside the while loop you need to check the CancellationPending property wether the value is true which indicates a call to the CancelAsync() method.
If CancellationPending evaluates to true, you would ( which you should have done already ) call one of the overloaded ReportProgress() (Docu) methods to set your ProgressBar value to the desired value.
EDIT: You should set the Cancel property of the DoWorkEventArgs to true so you can check the Cancelled property of the RunWorkerCompletedEventArgs inside the RunworkerCompletedevent.
You also shouldn not access any controls which lives in the UI thread. You better use the ProgressChanged(Docu) event.
See: BackgroundWorker Docu

Answer 2

Public Class Form1
Private iVal As Integer = 0
Private Sub bgw_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles bgw.DoWork
For iVal = iVal To 100 Step 1
bgw.ReportProgress(iVal)
Threading.Thread.Sleep(99)
If (bgw.CancellationPending = True) Then
e.Cancel = True
Exit For
End If
Next
End Sub
Private Sub bgw_ProgressChanged(ByVal sender As Object, ByVal e As System.ComponentModel.ProgressChangedEventArgs) Handles bgw.ProgressChanged
pbar.Value = e.ProgressPercentage
lblProgrss.Text = e.ProgressPercentage.ToString() & "%"
End Sub
Private Sub bgw_RunWorkerCompleted(ByVal sender As Object, ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles bgw.RunWorkerCompleted
If (e.Cancelled = True) Then
pic.Visible = False
pbar.Value = iVal
lblProgrss.Text = iVal & "%"
btnstart.Text = "Start"
btnstart.BackColor = Color.Green
Else
pic.Visible = False
btnstart.Text = "Start"
btnstart.BackColor = Color.Green
iVal = 0
End If
End Sub
Private Sub btnstart_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnstart.Click
If (btnstart.Text = "Start") Then
btnstart.Text = "Stop"
btnstart.BackColor = Color.Red
pic.Visible = True
bgw.RunWorkerAsync()
Else
If (bgw.IsBusy = True) Then
btnstart.Text = "Start"
btnstart.BackColor = Color.Green
bgw.CancelAsync()
End If
End If
End Sub
End Class