Background Worker ReportProgress not firing 2 - vb.net

Question

I am working on a Legacy app and this is driving me crazy, every example I have seen addressing this issue appears to do what I am doing but for some reason my reportProgress event refuses to fire:
Private _worker as BackgroundWorker
Private Sub btnEditCheckSymbol_Click (ByVal sender As Object, ByVal e As EventArgs) Handles btnEditCheckSymbol.Click
_worker = new BackgroundWorker()
_worker.WorkerSupportsCancellation = True
_worker.WorkerReportsProgress = True
AddHandler _worker.DoWork, AddressOf worker_DoWork
AddHandler _worker.ProgressChanged, AddressOf worker_ProgressChanged
AddHandler _worker.RunWorkerCompleted, AddressOf worker_RunWorkerCompleted
_worker.RunWorkerAsync()
'Other long running code
If _worker.IsBusy Then
_worker.CancelAsync()
End If
End Sub
Private Sub worker_DoWork(ByVal sender As Object, ByVal e As DoWorkEventArgs) _
For i As Integer = 60 To 0 step -1
If _worker.CancellationPending Then
e.Cancel = True
return
End If
_worker.ReportProgress(i)
Next
End Sub
Private Sub worker_ProgressChanged(ByVal sender As Object, ByVal e As ProgressChangedEventArgs) _
lbEditCheckSymbol.Invoke(
Sub ()
with lbEditCheckSymbol
.Items.Clear()
.Items.Add("Please wait for results: " + e.ProgressPercentage)
end With
End Sub)
Thread.Sleep(100)
End Sub
Private Sub worker_RunWorkerCompleted(ByVal sender As Object, ByVal e As RunWorkerCompletedEventArgs) _
with lbEditCheckSymbol
.Items.Clear()
If Not e.Cancelled then
lbEditCheckSymbol.Invoke(
Sub ()
with lbEditCheckSymbol
.Items.Add("Results should have arrived by now... um wait some more?")
end With
End Sub)
End If
end With
End Sub
The DoWork is called and it burns through the loop never invoking the ProgressChanged event, I checked in the debugger and the ProgressChanged is registered. I mostly work in C# so am I missing some VB voodoo here?
UPDATE
I have abandoned the use of the background worker in favor of the TPL library. Less code, easier to debug and I actually got it to work so win, win, win.

Answer 1

If you had better error handlers around your threaded work, you would catch the access violation when your background thread tries to access objects on the foreground thread. To reach-across threads like that, you need some delegates and use BeginInvoke instead of Invoke to call over to the right thread.
This code might not be perfect, but it should be pretty close
Private _worker as BackgroundWorker
Public Delegate Sub ProgressChangedDelegateType(percent As Integer)
Public Delegate Sub RunWorkerCompletedDelegateType(cancelled As Boolean)
Private progressChangedDelegate As ProgressChangedDelegateType
Private runWorkerCompletedDelegate AS RunWorkerCompletedDelegateType
Public Sub Form_Load()
'bind your delegates in your form load event or in the class constructor
progressChangedDelegate = AddressOf ProgressChanged
runWorkerCompletedDelegate = AddressOf RunWorkerCompleted
'and all of your other stuff in your form_load() event handler...
End Sub
Private Sub btnEditCheckSymbol_Click (ByVal sender As Object, ByVal e As EventArgs) Handles btnEditCheckSymbol.Click
_worker = new BackgroundWorker()
_worker.WorkerSupportsCancellation = True
_worker.WorkerReportsProgress = True
AddHandler _worker.DoWork, AddressOf worker_DoWork
AddHandler _worker.ProgressChanged, AddressOf worker_ProgressChanged
AddHandler _worker.RunWorkerCompleted, AddressOf worker_RunWorkerCompleted
_worker.RunWorkerAsync()
'Other long running code
If _worker.IsBusy Then
_worker.CancelAsync()
End If
End Sub
Private Sub worker_DoWork(ByVal sender As Object, ByVal e As DoWorkEventArgs) _
For i As Integer = 60 To 0 step -1
If _worker.CancellationPending Then
e.Cancel = True
return
End If
_worker.ReportProgress(i)
Next
End Sub
Private Sub worker_ProgressChanged(ByVal sender As Object, ByVal e As ProgressChangedEventArgs)
If lbEditCheckSymbol.InvokeRequired Then
BeginInvoke(progressChangedDelgate, {e.ProgressPercentage})
Else
ProgressChanged(e.ProgressPercentage)
End If
End Sub
Public Sub ProgressChanged(percent As Integer)
Try
with lbEditCheckSymbol
.Items.Clear()
.Items.Add("Please wait for results: " + percent.ToString())
end With
DoEvents() 'forces a UI update
Catch Ex As Exception
Debug.WriteLine(ex.message) 'put a breakpoint here, just in case
End Try
Thread.Sleep(100)
End Sub
Private Sub worker_RunWorkerCompleted(ByVal sender As Object, ByVal e As RunWorkerCompletedEventArgs) _
If lbEditCheckSymbol.InvokeRequired Then
BeginInvoke(runWorkerCompletedDelegate, {e.Cancelled})
Else
RunWorkerCompleted(e.Cancelled)
End If
End Sub
Public Sub RunWorkerCompleted(cancelled As Boolean)
Try
with lbEditCheckSymbol
.Items.Clear()
If Not cancelled then
.Items.Add("Results should have arrived by now... um wait some more?")
end With
DoEvents() 'Forces a UI update
Catch Ex As Exception
Debug.WriteLine(ex.message) 'put a breakpoint here, just in case
End Try
End Sub