[RESOLVED] Help with cancelling background worker?

Hello,

I have some background workers in my application and I'm having trouble trying to cancel them, so far I have the following...

Code:

---

If Backgroundworker1.IsBusy Then
            Backgroundworker1.CancelAsync()
            Backgroundworker1 = Nothing
        End If

If Backgroundworker2.IsBusy Then
            Backgroundworker2.CancelAsync()
            Backgroundworker2 = Nothing
        End If

If Backgroundworker3.IsBusy Then
            Backgroundworker3.CancelAsync()
            Backgroundworker3 = Nothing
        End If

---

Is there a way to kill all background workers in one go? Also, I have noticed that sometimes when I kill the background worker it still completes.

Would you recommend .dispose?

Many thanks.

http://msdn.microsoft.com/en-us/libr...(v=vs.95).aspx

Is a good example of how to cancel a background worker

The CancelAsync method just sets a flag in the BackgroundWorker to inform it that the task needs to be cancelled. You would need to check for CancellationPending inside the procedure the BackgroundWorker is running, and cancel out accordingly. If you don't do, it will continue to run normally.

Are you sure you are doing everything correctly?

To answer the first part of your question: How to cancel all the BackgroundWorkers,

You can do it like this:

vb.net Code:

'' Declare an array of BackgroundWorkers
Dim MyBackgroundWorkers() As BackgroundWorker
 
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    '' add all your BackgroundWorkers to the array
    MyBackgroundWorkers = New BackgroundWorker() {BackgroundWorker1, BackgroundWorker2, BackgroundWorker3, BackgroundWorker4, BackgroundWorker5}
End Sub
 
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    '' now you can Cancel all of them in a loop
    For Each bgw In MyBackgroundWorkers
        If bgw.IsBusy Then
            bgw.CancelAsync()
        End If
    Next
End Sub

This is assuming that your BackgroundWorkers are controls you added from the toolbox at design time. If it was declared and added from code, you would need to make appropriate modifications in the Form_Load code.

Calling CancelAsync doesn't cancel a BackgroundWorker's task. It simply requests that the task be cancelled. It's up to you to write code in the DoWork event handler to detect that request and duly end the task. For several examples of using the BackgroundWorker, including cancellation, follow the CodeBank link in my signature and check out my post on Using The BackgroundWorker.

Many thanks guys for your help. Jmcilhinney, the codebank was very helpful and I have figured out how to do the cancel using your example.

I have decided to take your advice and not bother with many background workers and do the coding within the one BG, What I was trying to do was when the user clicks cancel then I wanted to kill the background worker, move the folder to another location and delete the folder but it looks like something has hold of a process in one of the files in the folders so I cant kill it.

Do you know if there is anything I could use to kill a folder and any process that might be in use in that folder? I use the IO delete directory.

Code:

---

    If My.Computer.FileSystem.DirectoryExists(“Path”) = True Then
            My.Computer.FileSystem.DeleteDirectory“Path”), FileIO.DeleteDirectoryOption.DeleteAllContents)
        End If

---

While cancelling out from a BackgroundWorker, ensure that you close your resources properly. Probably you had a file open which you didn't close when you cancelled out of the BackgroundWorker.

Pradeep is quite correct. It's for this reason that you should use a Using block to create short-lived disposable objects, e.g. a FileStream or StreamReader. That way, the object is disposed when you leave the Using block, no matter how you leave it. Disposing an object that opens a file will close the file.

You can have a look at this thread to get an overview of how a BackgroundWorker should be properly coded:

http://www.vbforums.com/showthread.php?t=680130

You didn't like my CodeBank examples Pradeep? :)

Thanks Pradeep & JM.


I have pasted the coding that goes in my background worker, its pretty simple really just some process commands and some coding to filter the data.

Code:

---


‘The following coding is in my Backgroundworker Do Work

 myProcess = New Process

  Me.label1.Text = "Run first command"


        Dim sid As String
        ‘ Start My process coding
        Dim sidIn As System.IO.StreamWriter = myProcess.StandardInput
        Dim sidOut As System.IO.StreamReader = myProcess.StandardOutput
        Dim sidErr As System.IO.StreamReader = myProcess.StandardError

        sidIn.AutoFlush = True

        sidIn.Write("Run First Command" & System.Environment.NewLine)
        sidIn.Write("exit" & System.Environment.NewLine)

        sid = sidOut.ReadToEnd()

        sidIn.Close()
        sidOut.Close()
        sidErr.Close()
        myProcess.Close()

  Me.label1.Text = "Edit the data"

       
        Dim sourcefile As String = IO.Path.Combine("Path")
        Dim rdrfile As IO.StreamReader = IO.File.OpenText(sourcefile)
        Dim strtemp() As String
        Dim FileLines As New List(Of String)
        Do While rdrfile.Peek <> -1
            FileLines.Add(rdrfile.ReadLine)
        Loop
        rdrfile.Close()

        Dim writer As IO.StreamWriter = New IO.StreamWriter(sourcefile, False)
        Dim Columns As New List(Of String)

        For Each Str As String In FileLines
            strtemp = Str.Split(" "c)
            If Trim(strtemp(0)) = "FILENO" Then writer.Write(strtemp(11).Trim & vbCrLf)
        Next

        For Each filtereditem As String In Columns
            writer.Write(filtereditem & vbCrLf)
        Next

        writer.Close()
        FileLines.Clear()

        Me.label1.Text = "Run second command"

     
        myProcess = New Process
      ‘ Start My process coding
        Dim smed As String
     

        Dim smedIn As System.IO.StreamWriter = myProcess.StandardInput
        Dim smedOut As System.IO.StreamReader = myProcess.StandardOutput
        Dim smedErr As System.IO.StreamReader = myProcess.StandardError

        smedIn.AutoFlush = True
        smedIn.Write("Run Second Command" & System.Environment.NewLine)
        smedIn.Write("exit" & System.Environment.NewLine)

        smed = smedOut.ReadToEnd()

        smedIn.Close()
        smedOut.Close()
        smedErr.Close()
        myProcess.Close()

        Me.label1.Text = "Run Third Command"

        myProcess = New Process

        Dim sfre As String
      ‘ Start My process coding
        Dim sfreIn As System.IO.StreamWriter = myProcess.StandardInput
        Dim sfreOut As System.IO.StreamReader = myProcess.StandardOutput
        Dim sfreErr As System.IO.StreamReader = myProcess.StandardError

        sfreIn.AutoFlush = True
        sfreIn.Write("Run Third Command” & System.Environment.NewLine)
        sfreIn.Write("exit" & System.Environment.NewLine)

        sfre = sfreOut.ReadToEnd()

        sfreIn.Close()
        sfreOut.Close()
        sfreErr.Close()
        myProcess.Close()

        Me.label1.Text = "Run Fourth Command"

        myProcess = New Process

        Dim scl As String

        Dim sclIn As System.IO.StreamWriter = myProcess.StandardInput
        Dim sclOut As System.IO.StreamReader = myProcess.StandardOutput
        Dim sclErr As System.IO.StreamReader = myProcess.StandardError

        sclIn.AutoFlush = True
        sclIn.Write("Run Fourth Command" & System.Environment.NewLine)
        sclIn.Write("exit" & System.Environment.NewLine)

        scl = sclOut.ReadToEnd()

        sclIn.Close()
        sclOut.Close()
        sclErr.Close()
        myProcess.Close()

        Me.label1.Text = "Edit the Data"

        Dim Open As String = IO.Path.Combine("Path")
        Dim Save As String = IO.Path.Combine("Path")

        Dim sb As New System.Text.StringBuilder

        Dim Lines =
            (From line In IO.File.ReadAllLines(Open)
                Where line.Length > 0
Select line).ToList

        For Each item In Lines
            Dim TempItem = item
            Dim Column1 = TempItem.Substring(0, TempItem.IndexOf(" "))
            TempItem = TempItem.Replace(Column1, "").Trim
            Dim Column2 = TempItem.Substring(0, 20)

            TempItem = TempItem.Replace(Column2, "").Trim

            Dim Parts = System.Text.RegularExpressions.Regex.Replace(TempItem.TrimStart, " {2,}", ",").Replace(" ", ",").Split(","c)

            sb.AppendLine(
                String.Format("{0}{1}",
                              Column1.PadRight(100, " "c),
                              Column2.PadRight(100, " "c),))

        Next

        IO.File.WriteAllText(Save, sb.ToString)

        Dim inputFile = Regex.Replace(IO.File.ReadAllText(Save), "[ ]{2,}", " ")
        IO.File.WriteAllText(Save, inputFile)


    Dim worker As System.ComponentModel.BackgroundWorker = DirectCast(sender, System.ComponentModel.BackgroundWorker)


        If worker.CancellationPending Then
            e.Cancel = True

  sidIn.Close()
        sidOut.Close()
        sidErr.Close()
        myProcess.Close()

        writer.Close()
        FileLines.Clear()


.        smedIn.Close()
        smedOut.Close()
        smedErr.Close()
        myProcess.Close()

        sfreIn.Close()
        sfreOut.Close()
        sfreErr.Close()
        myProcess.Close()


        sclIn.Close()
        sclOut.Close()
        sclErr.Close()
        myProcess.Close()

IO.File.WriteAllText(Save, sb.ToString)


        End If

---

As you can see I’ve tried to close all connections when cancellation pending.

Code:

---

  myProcess.StartInfo.FileName = "c:\windows\system32\cmd.exe"
        myProcess.StartInfo.UseShellExecute = False
        myProcess.StartInfo.CreateNoWindow = True
        myProcess.StartInfo.RedirectStandardInput = True
        myProcess.StartInfo.RedirectStandardOutput = True
        myProcess.StartInfo.RedirectStandardError = True
        myProcess.Start()

---

Thats how i start my process

Quote:

---

Originally Posted by jmcilhinney

You didn't like my CodeBank examples Pradeep? :)

---

oooohhh :blush:
My bad! I completely forgot about that one when I was posting my sample.

It looks like that's far better than my sample and also has many examples in the followup posts :)

@frankwhite: Here's the link:
http://www.vbforums.com/showthread.php?t=471889

The problem is:
You have used the worker.CancellationPending in just the opposite way of how it should be used.
Currently, you have your code to release the resources (close method calls) inside the If worker.CancellationPending Then ... End If block. This means that your resources will be closed only if you cancel and not otherwise.

And your BackgroundWorker will never effectively cancel the Work because you never checked for CancellationPending in the rest of the code.

Do the following things:
1. Move the code to close your resources outside the IF..END IF block.
2. Earlier in the code, check for CancellationPending and cut short your Work accordingly. Loops are usually the best places to do this.
Those code blocks (inside the loops) would look something like this:

Code:

---

If worker.CancellationPending Then
    e.Cancel = True
    Exit Do    ' or Exit For etc. as the case may be.
End If

---

Post back here if you still face problems.

I think I understand, do you mean have the following coding in each section of the background worker?

Code:

---

    If worker.CancellationPending Then
            e.Cancel = True
        End If

---

When you say Loops, do you mean in each section of the coding?

Basically you need to break up the work in your event handler into logical tasks. If you're using a loop, as many examples do, then each iteration of the loop is a task. You need to test CancellationPending between each pair of tasks and, if it's True, don't perform any further tasks. As suggested, cleanup must be performed whether the background work is cancelled or not. If each "section" you're talking about is a logical task then yes, you must check for cancellation after each section. You must also NOT execute any more sections.

Quote:

---

Originally Posted by frankwhite

I think I understand, do you mean have the following coding in each section of the background worker?

Code:

---

    If worker.CancellationPending Then
            e.Cancel = True
        End If

---

When you say Loops, do you mean in each section of the coding?

---

Checking for once in each loop would do.
Don't forget to put the the Exit Do / Exit For etc. Without that it would be worthless.

Pradeep,

Do you mean something like the following?

Code:

---

       
        Dim intCount As Integer = 0

     
        Do While intCount < 1

    myProcess = New Process

        Dim sid As String
        myProcess.StartInfo.FileName = "c:\windows\system32\cmd.exe"
        myProcess.StartInfo.UseShellExecute = False
        myProcess.StartInfo.CreateNoWindow = True
        myProcess.StartInfo.RedirectStandardInput = True
        myProcess.StartInfo.RedirectStandardOutput = True
        myProcess.StartInfo.RedirectStandardError = True
        myProcess.Start()

        Dim sidIn As System.IO.StreamWriter = myProcess.StandardInput
        Dim sidOut As System.IO.StreamReader = myProcess.StandardOutput
        Dim sidErr As System.IO.StreamReader = myProcess.StandardError

        sidIn.AutoFlush = True

        sidIn.Write("Run first command" & lbljobid.Text & "ImageID.txt" & System.Environment.NewLine)
        sidIn.Write("exit" & System.Environment.NewLine)

        sid = sidOut.ReadToEnd()

        sidIn.Close()
        sidOut.Close()
        sidErr.Close()
        myProcess.Close()



            'Increment intCount by 1
            intCount += 1

If worker.CancellationPending Then
    e.Cancel = True
    Exit Do   
End If

            End If

---

Edit* and so on and so on for the other sections?

Quote:

---

Originally Posted by frankwhite

Pradeep,

Do you mean something like the following?

Edit* and so on and so on for the other sections?

---

Yes you did it right :thumb:

Just repeat it for all the other loops. :)

Have a look at this:

vb.net Code:

Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
    '' move this to the start of your DoWork event procedure
    Dim worker As System.ComponentModel.BackgroundWorker = DirectCast(sender, System.ComponentModel.BackgroundWorker)
 
    '' your other code
 
    Do While rdrfile.Peek <> -1
        '' your other code
 
        If worker.CancellationPending Then Exit Do
    Loop
 
    '' your other code
 
    For Each Str As String In FileLines
        '' your other code
 
        If worker.CancellationPending Then Exit For
    Next
 
    For Each filtereditem As String In Columns
        '' your other code
 
        If worker.CancellationPending Then Exit For
    Next
 
    '' your other code
 
    For Each item In Lines
        '' your other code
 
        If worker.CancellationPending Then Exit For
    Next
 
    '' your other code
 
 
    '' just before End Sub
    If worker.CancellationPending Then e.Cancel = True
End Sub

thanks,

when you say ''your other code do you mean still include loops for the other code?

One more question I have is i forgot to add the 'loop' to the previous code, is something like the following correct?

Code:

---

    Dim intCount As Integer = 0


        Do While intCount < 1


        Loop

        myProcess = New Process
''....then the rest of the coding

  If worker.CancellationPending Then
            e.Cancel = True
            Exit Do
        End If

---

But I get Error 2 'Exit Do' can only appear inside a 'Do' statement.

Quote:

---

Originally Posted by Pradeep1210

Have a look at this:

vb.net Code:

Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
    '' move this to the start of your DoWork event procedure
    Dim worker As System.ComponentModel.BackgroundWorker = DirectCast(sender, System.ComponentModel.BackgroundWorker)
 
    '' your other code
 
    Do While rdrfile.Peek <> -1
        '' your other code
 
        If worker.CancellationPending Then Exit Do
    Loop
 
    '' your other code
 
    For Each Str As String In FileLines
        '' your other code
 
        If worker.CancellationPending Then Exit For
    Next
 
    For Each filtereditem As String In Columns
        '' your other code
 
        If worker.CancellationPending Then Exit For
    Next
 
    '' your other code
 
    For Each item In Lines
        '' your other code
 
        If worker.CancellationPending Then Exit For
    Next
 
    '' your other code
 
 
    '' just before End Sub
    If worker.CancellationPending Then e.Cancel = True
End Sub

---

That's not quite right because that is still going to do the work in the first iteration of every loop even if the work is cancelled right at the start. As I said, if you detect a cancellation request then you need to make sure that you don't do any more work.

Thanks Jmcilhinney, is there a suggestion you could make on the best way to do this?

so If cancellationpending = True then dont run any more coding for the background worker do work event?

How about the obvious:

vb Code:

If Not e.CancellationPending Then
    'Do the work here.
End If

Quote:

---

Originally Posted by jmcilhinney

That's not quite right because that is still going to do the work in the first iteration of every loop even if the work is cancelled right at the start. As I said, if you detect a cancellation request then you need to make sure that you don't do any more work.

---

hmm.. yes :)

So it goes like this:

Code:

---

Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
    '' move this to the start of your DoWork event procedure
    Dim worker As System.ComponentModel.BackgroundWorker = DirectCast(sender, System.ComponentModel.BackgroundWorker)
 
    '' your other code
 
    Do While rdrfile.Peek <> -1
        If worker.CancellationPending Then Exit Do

        '' your other code
    Loop
 
    '' your other code
 
    For Each Str As String In FileLines
        If worker.CancellationPending Then Exit For

        '' your other code
 
    Next
 
    For Each filtereditem As String In Columns
        If worker.CancellationPending Then Exit For

        '' your other code
 
    Next
 
    '' your other code
 
    For Each item In Lines
        If worker.CancellationPending Then Exit For

        '' your other code
 
    Next
 
    '' your other code
 
 
    '' just before End Sub
    If worker.CancellationPending Then e.Cancel = True
End Sub

---

Hi Pradeep,

so something like so?

Code:

---

Dim worker As System.ComponentModel.BackgroundWorker = DirectCast(sender, System.ComponentModel.BackgroundWorker)

        Dim intCount As Integer = 0

        Do While intCount < 1

        Loop

        myProcess = New Process

        Me.Label1.Text = "Run first command"


        Dim sid As String
        ' Start My process coding
        Dim sidIn As System.IO.StreamWriter = myProcess.StandardInput
        Dim sidOut As System.IO.StreamReader = myProcess.StandardOutput
        Dim sidErr As System.IO.StreamReader = myProcess.StandardError

        sidIn.AutoFlush = True

        sidIn.Write("Run First Command" & System.Environment.NewLine)
        sidIn.Write("exit" & System.Environment.NewLine)

        sid = sidOut.ReadToEnd()

        sidIn.Close()
        sidOut.Close()
        sidErr.Close()
        myProcess.Close()

        'Increment intCount by 1
        intCount += 1

        If worker.CancellationPending Then
            e.Cancel = True
            Exit Sub
        End If



        Me.Label1.Text = "Edit the data"


        Dim sourcefile As String = IO.Path.Combine("Path")
        Dim rdrfile As IO.StreamReader = IO.File.OpenText(sourcefile)
        Dim strtemp() As String
        Dim FileLines As New List(Of String)


        Do While rdrfile.Peek <> -1
            If worker.CancellationPending Then Exit Do

            FileLines.Add(rdrfile.ReadLine)
        Loop

        rdrfile.Close()

        Dim writer As IO.StreamWriter = New IO.StreamWriter(sourcefile, False)
        Dim Columns As New List(Of String)


        For Each Str As String In FileLines
            If worker.CancellationPending Then Exit For

            strtemp = Str.Split(" "c)
            If Trim(strtemp(0)) = "FILENO" Then writer.Write(strtemp(11).Trim & vbCrLf)
        Next

        For Each filtereditem As String In Columns
            If worker.CancellationPending Then Exit For
            writer.Write(filtereditem & vbCrLf)

        Next

        writer.Close()
        FileLines.Clear()

        Do While intCount < 1

        Loop

        myProcess = New Process
        ' Start My process coding
        Dim smed As String


        Dim smedIn As System.IO.StreamWriter = myProcess.StandardInput
        Dim smedOut As System.IO.StreamReader = myProcess.StandardOutput
        Dim smedErr As System.IO.StreamReader = myProcess.StandardError

        smedIn.AutoFlush = True
        smedIn.Write("Run Second Command" & System.Environment.NewLine)
        smedIn.Write("exit" & System.Environment.NewLine)

        smed = smedOut.ReadToEnd()

        smedIn.Close()
        smedOut.Close()
        smedErr.Close()
        myProcess.Close()

        'Increment intCount by 1
        intCount += 1

        If worker.CancellationPending Then
            e.Cancel = True
            Exit Sub
        End If

        Do While intCount < 1

        Loop

        Me.Label1.Text = "Run Third Command"

        myProcess = New Process

        Dim sfre As String
        ' Start My process coding
        Dim sfreIn As System.IO.StreamWriter = myProcess.StandardInput
        Dim sfreOut As System.IO.StreamReader = myProcess.StandardOutput
        Dim sfreErr As System.IO.StreamReader = myProcess.StandardError

        sfreIn.AutoFlush = True
        sfreIn.Write("Run Third Command" & System.Environment.NewLine)
        sfreIn.Write("exit" & System.Environment.NewLine)

        sfre = sfreOut.ReadToEnd()

        sfreIn.Close()
        sfreOut.Close()
        sfreErr.Close()
        myProcess.Close()

        'Increment intCount by 1
        intCount += 1

        If worker.CancellationPending Then
            e.Cancel = True
            Exit Sub
        End If

        Do While intCount < 1

        Loop

        Me.Label1.Text = "Run Fourth Command"

        myProcess = New Process

        Dim scl As String

        Dim sclIn As System.IO.StreamWriter = myProcess.StandardInput
        Dim sclOut As System.IO.StreamReader = myProcess.StandardOutput
        Dim sclErr As System.IO.StreamReader = myProcess.StandardError

        sclIn.AutoFlush = True
        sclIn.Write("Run Fourth Command" & System.Environment.NewLine)
        sclIn.Write("exit" & System.Environment.NewLine)

        scl = sclOut.ReadToEnd()

        sclIn.Close()
        sclOut.Close()
        sclErr.Close()
        myProcess.Close()

        'Increment intCount by 1
        intCount += 1

        If worker.CancellationPending Then
            e.Cancel = True
            Exit Sub
        End If

        Me.Label1.Text = "Edit the Data"

        Dim Open As String = IO.Path.Combine("Path")
        Dim Save As String = IO.Path.Combine("Path")

        Dim sb As New System.Text.StringBuilder

        Dim Lines =
            (From line In IO.File.ReadAllLines(Open)
                Where line.Length > 0
        Select line).ToList


        For Each item In Lines
            If worker.CancellationPending Then Exit For

            Dim TempItem = item
            Dim Column1 = TempItem.Substring(0, TempItem.IndexOf(" "))
            TempItem = TempItem.Replace(Column1, "").Trim
            Dim Column2 = TempItem.Substring(0, 20)

            TempItem = TempItem.Replace(Column2, "").Trim

            Dim Parts = System.Text.RegularExpressions.Regex.Replace(TempItem.TrimStart, " {2,}", ",").Replace(" ", ",").Split(","c)

            sb.AppendLine(
                String.Format("{0}{1}",
                              Column1.PadRight(100, " "c),
                              Column2.PadRight(100, " "c), ))


        Next

        IO.File.WriteAllText(Save, sb.ToString)

        Dim inputFile = Regex.Replace(IO.File.ReadAllText(Save), "[ ]{2,}", " ")
        IO.File.WriteAllText(Save, inputFile)


        If worker.CancellationPending Then e.Cancel = True

---

It looks like you have introduced a few extra infinite looks while making the code changes. Have a look at the highlighted code below.

I was expecting your rest of the code to remain same except for those single line codes here and there I showed you in the previous post.

Code:

---

Dim worker As System.ComponentModel.BackgroundWorker = DirectCast(sender, System.ComponentModel.BackgroundWorker)

        Dim intCount As Integer = 0

        Do While intCount < 1

        Loop

        myProcess = New Process

        Me.Label1.Text = "Run first command"


        Dim sid As String
        ' Start My process coding
        Dim sidIn As System.IO.StreamWriter = myProcess.StandardInput
        Dim sidOut As System.IO.StreamReader = myProcess.StandardOutput
        Dim sidErr As System.IO.StreamReader = myProcess.StandardError

        sidIn.AutoFlush = True

        sidIn.Write("Run First Command" & System.Environment.NewLine)
        sidIn.Write("exit" & System.Environment.NewLine)

        sid = sidOut.ReadToEnd()

        sidIn.Close()
        sidOut.Close()
        sidErr.Close()
        myProcess.Close()

        'Increment intCount by 1
        intCount += 1

        If worker.CancellationPending Then
            e.Cancel = True
            Exit Sub
        End If



        Me.Label1.Text = "Edit the data"


        Dim sourcefile As String = IO.Path.Combine("Path")
        Dim rdrfile As IO.StreamReader = IO.File.OpenText(sourcefile)
        Dim strtemp() As String
        Dim FileLines As New List(Of String)


        Do While rdrfile.Peek <> -1
            If worker.CancellationPending Then Exit Do

            FileLines.Add(rdrfile.ReadLine)
        Loop

        rdrfile.Close()

        Dim writer As IO.StreamWriter = New IO.StreamWriter(sourcefile, False)
        Dim Columns As New List(Of String)


        For Each Str As String In FileLines
            If worker.CancellationPending Then Exit For

            strtemp = Str.Split(" "c)
            If Trim(strtemp(0)) = "FILENO" Then writer.Write(strtemp(11).Trim & vbCrLf)
        Next

        For Each filtereditem As String In Columns
            If worker.CancellationPending Then Exit For
            writer.Write(filtereditem & vbCrLf)

        Next

        writer.Close()
        FileLines.Clear()

        Do While intCount < 1

        Loop

        myProcess = New Process
        ' Start My process coding
        Dim smed As String


        Dim smedIn As System.IO.StreamWriter = myProcess.StandardInput
        Dim smedOut As System.IO.StreamReader = myProcess.StandardOutput
        Dim smedErr As System.IO.StreamReader = myProcess.StandardError

        smedIn.AutoFlush = True
        smedIn.Write("Run Second Command" & System.Environment.NewLine)
        smedIn.Write("exit" & System.Environment.NewLine)

        smed = smedOut.ReadToEnd()

        smedIn.Close()
        smedOut.Close()
        smedErr.Close()
        myProcess.Close()

        'Increment intCount by 1
        intCount += 1

        If worker.CancellationPending Then
            e.Cancel = True
            Exit Sub
        End If

        Do While intCount < 1

        Loop

        Me.Label1.Text = "Run Third Command"

        myProcess = New Process

        Dim sfre As String
        ' Start My process coding
        Dim sfreIn As System.IO.StreamWriter = myProcess.StandardInput
        Dim sfreOut As System.IO.StreamReader = myProcess.StandardOutput
        Dim sfreErr As System.IO.StreamReader = myProcess.StandardError

        sfreIn.AutoFlush = True
        sfreIn.Write("Run Third Command" & System.Environment.NewLine)
        sfreIn.Write("exit" & System.Environment.NewLine)

        sfre = sfreOut.ReadToEnd()

        sfreIn.Close()
        sfreOut.Close()
        sfreErr.Close()
        myProcess.Close()

        'Increment intCount by 1
        intCount += 1

        If worker.CancellationPending Then
            e.Cancel = True
            Exit Sub
        End If

        Do While intCount < 1

        Loop

        Me.Label1.Text = "Run Fourth Command"

        myProcess = New Process

        Dim scl As String

        Dim sclIn As System.IO.StreamWriter = myProcess.StandardInput
        Dim sclOut As System.IO.StreamReader = myProcess.StandardOutput
        Dim sclErr As System.IO.StreamReader = myProcess.StandardError

        sclIn.AutoFlush = True
        sclIn.Write("Run Fourth Command" & System.Environment.NewLine)
        sclIn.Write("exit" & System.Environment.NewLine)

        scl = sclOut.ReadToEnd()

        sclIn.Close()
        sclOut.Close()
        sclErr.Close()
        myProcess.Close()

        'Increment intCount by 1
        intCount += 1

        If worker.CancellationPending Then
            e.Cancel = True
            Exit Sub
        End If

        Me.Label1.Text = "Edit the Data"

        Dim Open As String = IO.Path.Combine("Path")
        Dim Save As String = IO.Path.Combine("Path")

        Dim sb As New System.Text.StringBuilder

        Dim Lines =
            (From line In IO.File.ReadAllLines(Open)
                Where line.Length > 0
        Select line).ToList


        For Each item In Lines
            If worker.CancellationPending Then Exit For

            Dim TempItem = item
            Dim Column1 = TempItem.Substring(0, TempItem.IndexOf(" "))
            TempItem = TempItem.Replace(Column1, "").Trim
            Dim Column2 = TempItem.Substring(0, 20)

            TempItem = TempItem.Replace(Column2, "").Trim

            Dim Parts = System.Text.RegularExpressions.Regex.Replace(TempItem.TrimStart, " {2,}", ",").Replace(" ", ",").Split(","c)

            sb.AppendLine(
                String.Format("{0}{1}",
                              Column1.PadRight(100, " "c),
                              Column2.PadRight(100, " "c), ))


        Next

        IO.File.WriteAllText(Save, sb.ToString)

        Dim inputFile = Regex.Replace(IO.File.ReadAllText(Save), "[ ]{2,}", " ")
        IO.File.WriteAllText(Save, inputFile)


        If worker.CancellationPending Then e.Cancel = True

---

Oh ok sorry Pradeep,

I have removed the extra coding.

I was under the impression that each section of coding had to be looped and if cancel was appending from any loop then it would all cancel? I'm sorry but its just I can see some sections that have no loops/do while like section 1, 2, 3 4 and 5?

The bg worker has 6 sections:-

Section 1

Code:

---

Dim intCount As Integer = 0
        Me.Label1.Text = "Run first command"
        myProcess = New Process

        Dim sid As String
        Dim sidIn As System.IO.StreamWriter = myProcess.StandardInput
        Dim sidOut As System.IO.StreamReader = myProcess.StandardOutput
        Dim sidErr As System.IO.StreamReader = myProcess.StandardError
        sidIn.AutoFlush = True
        sidIn.Write("Run First Command" & System.Environment.NewLine)
        sidIn.Write("exit" & System.Environment.NewLine)
        sid = sidOut.ReadToEnd()
        sidIn.Close()
        sidOut.Close()
        sidErr.Close()
        myProcess.Close()
        'Increment intCount by 1
        intCount += 1

        If worker.CancellationPending Then
            e.Cancel = True
            Exit Sub
        End If

---

Section 2

Code:

---

Me.Label1.Text = "Edit the data"
        Dim sourcefile As String = IO.Path.Combine("Path")
        Dim rdrfile As IO.StreamReader = IO.File.OpenText(sourcefile)
        Dim strtemp() As String
        Dim FileLines As New List(Of String)
        Do While rdrfile.Peek <> -1
            If worker.CancellationPending Then Exit Do
            FileLines.Add(rdrfile.ReadLine)
        Loop
        rdrfile.Close()
        Dim writer As IO.StreamWriter = New IO.StreamWriter(sourcefile, False)
        Dim Columns As New List(Of String)
        For Each Str As String In FileLines
            If worker.CancellationPending Then Exit For
            strtemp = Str.Split(" "c)
            If Trim(strtemp(0)) = "FILENO" Then writer.Write(strtemp(11).Trim & vbCrLf)
        Next
        For Each filtereditem As String In Columns
            If worker.CancellationPending Then Exit For
            writer.Write(filtereditem & vbCrLf)
        Next
        writer.Close()
        FileLines.Clear()

---

Section 3

Code:

---

Me.Label1.Text = "Run Second Command"

        myProcess = New Process
        Dim smed As String
        Dim smedIn As System.IO.StreamWriter = myProcess.StandardInput
        Dim smedOut As System.IO.StreamReader = myProcess.StandardOutput
        Dim smedErr As System.IO.StreamReader = myProcess.StandardError
        smedIn.AutoFlush = True
        smedIn.Write("Run Second Command" & System.Environment.NewLine)
        smedIn.Write("exit" & System.Environment.NewLine)
        smed = smedOut.ReadToEnd()
        smedIn.Close()
        smedOut.Close()
        smedErr.Close()
        myProcess.Close()

        'Increment intCount by 1
        intCount += 1

        If worker.CancellationPending Then
            e.Cancel = True
            Exit Sub
        End If

---

Section 4

Code:

---

Me.Label1.Text = "Run Third Command"

        myProcess = New Process

        Dim sfre As String
        ' Start My process coding
        Dim sfreIn As System.IO.StreamWriter = myProcess.StandardInput
        Dim sfreOut As System.IO.StreamReader = myProcess.StandardOutput
        Dim sfreErr As System.IO.StreamReader = myProcess.StandardError

        sfreIn.AutoFlush = True
        sfreIn.Write("Run Third Command" & System.Environment.NewLine)
        sfreIn.Write("exit" & System.Environment.NewLine)

        sfre = sfreOut.ReadToEnd()

        sfreIn.Close()
        sfreOut.Close()
        sfreErr.Close()
        myProcess.Close()

        'Increment intCount by 1
        intCount += 1

        If worker.CancellationPending Then
            e.Cancel = True
            Exit Sub
        End If

---

Section 5

Code:

---

Me.Label1.Text = "Run Fourth Command"

        myProcess = New Process

        Dim scl As String

        Dim sclIn As System.IO.StreamWriter = myProcess.StandardInput
        Dim sclOut As System.IO.StreamReader = myProcess.StandardOutput
        Dim sclErr As System.IO.StreamReader = myProcess.StandardError

        sclIn.AutoFlush = True
        sclIn.Write("Run Fourth Command" & System.Environment.NewLine)
        sclIn.Write("exit" & System.Environment.NewLine)

        scl = sclOut.ReadToEnd()

        sclIn.Close()
        sclOut.Close()
        sclErr.Close()
        myProcess.Close()

        'Increment intCount by 1
        intCount += 1

        If worker.CancellationPending Then
            e.Cancel = True
            Exit Sub
        End If

---

Section 6

Code:

---

Me.Label1.Text = "Edit the Data"

        Dim Open As String = IO.Path.Combine("Path")
        Dim Save As String = IO.Path.Combine("Path")

        Dim sb As New System.Text.StringBuilder

        Dim Lines =
            (From line In IO.File.ReadAllLines(Open)
                Where line.Length > 0
        Select line).ToList


        For Each item In Lines
            If worker.CancellationPending Then Exit For

            Dim TempItem = item
            Dim Column1 = TempItem.Substring(0, TempItem.IndexOf(" "))
            TempItem = TempItem.Replace(Column1, "").Trim
            Dim Column2 = TempItem.Substring(0, 20)

            TempItem = TempItem.Replace(Column2, "").Trim

            Dim Parts = System.Text.RegularExpressions.Regex.Replace(TempItem.TrimStart, " {2,}", ",").Replace(" ", ",").Split(","c)

            sb.AppendLine(
                String.Format("{0}{1}",
                              Column1.PadRight(100, " "c),
                              Column2.PadRight(100, " "c), ))


        Next

        IO.File.WriteAllText(Save, sb.ToString)

        Dim inputFile = Regex.Replace(IO.File.ReadAllText(Save), "[ ]{2,}", " ")
        IO.File.WriteAllText(Save, inputFile)


        If worker.CancellationPending Then e.Cancel = True

---

Also one more thing I use Exit Sub rather than Exit Do as that was showing an error, is that ok?

ok. That's great.

Now put each section code inside the If NOT worker.CancellationPending Then ... End If block.

e.g.

Code:

---

If Not worker.CancellationPending Then

  '' section 1 code goes here...

End If
If Not worker.CancellationPending Then

  '' section 2 code goes here...

End If

.... repeat for all sections....


'' Finally after your last section (i.e. just before End Sub)
If worker.CancellationPending Then e.Cancel = True

---

Ensure that each section is complete in itself. It should not have any dependency on any other section. So for example any file opened in one section should be closed in the same section itself etc.

Put this code and you should be all set to go. :)

Many thanks Pradeep.

Just one more thing I forgot to mention that I had a section 7, it is very small. I have included it below, is it ok?

Section 7

Code:

---

If Not worker.CancellationPending Then
dim contents as string = IO.File.ReadAllText("Path 1")
IO.File.AppendAllText("Path 2", vbCrLf & contents)
End If

If worker.CancellationPending Then e.Cancel = True

---

So everything is working alright now? :)

Thank you a million Pradeep & JM. :thumb:

Pradeep,

Sorry one final question.

One of my commands works like this, IF its cancelled then I have to run another command to undo what I have just done - this will only need to run if a text file has been created. Do you think the following coding looks ok? I have tested it and it does seem ok.

Code:

---

  If Not worker.CancellationPending Then

            Me.lbl1.Text = "Run third command"

            'Create a new process 
            myProcess = New Process

            Dim sfre As String
            myProcess.StartInfo.FileName = "c:\windows\system32\cmd.exe"
            myProcess.StartInfo.UseShellExecute = False
            myProcess.StartInfo.CreateNoWindow = True
            myProcess.StartInfo.RedirectStandardInput = True
            myProcess.StartInfo.RedirectStandardOutput = True
            myProcess.StartInfo.RedirectStandardError = True
            myProcess.Start()

            Dim sfreIn As System.IO.StreamWriter = myProcess.StandardInput
            Dim sfreOut As System.IO.StreamReader = myProcess.StandardOutput
            Dim sfreErr As System.IO.StreamReader = myProcess.StandardError

            sfreIn.AutoFlush = True
            sfreIn.Write("command1" & System.Environment.NewLine)
            sfreIn.Write("exit" & System.Environment.NewLine)

            sfre = sfreOut.ReadToEnd()

            sfreIn.Close()
            sfreOut.Close()
            sfreErr.Close()
            myProcess.Close()

            'Increment intCount by 1
            intCount += 1


            If worker.CancellationPending Then
                e.Cancel = True
         
   
                If System.IO.File.Exists("Path") = True Then
                Me.lbl1.Text = "Run other command"
                    myProcess = New Process

                    Dim sfree As String
                    myProcess.StartInfo.FileName = "c:\windows\system32\cmd.exe"
                    myProcess.StartInfo.UseShellExecute = False
                    myProcess.StartInfo.CreateNoWindow = True
                    myProcess.StartInfo.RedirectStandardInput = True
                    myProcess.StartInfo.RedirectStandardOutput = True
                    myProcess.StartInfo.RedirectStandardError = True
                    myProcess.Start()

                    Dim sfreeIn As System.IO.StreamWriter = myProcess.StandardInput
                    Dim sfreeOut As System.IO.StreamReader = myProcess.StandardOutput
                    Dim sfreeErr As System.IO.StreamReader = myProcess.StandardError

                    sfreeIn.AutoFlush = True
                    sfreeIn.Write("Command2" & System.Environment.NewLine)
                    sfreeIn.Write("exit" & System.Environment.NewLine)

                    sfree = sfreeOut.ReadToEnd()

                    sfreeIn.Close()
                    sfreeOut.Close()
                    sfreeErr.Close()
                    myProcess.Close()

                    'Increment intCount by 1
                    intCount += 1
                End If

                Exit Sub
            End If

        End If

---

That would work. But I think making it as a separate section would be better.
You have already divided your code into 7 sections. So you can add this as 8th one which does the rollback operation. :)

thanks mate.