Immediate Termination of a BackgroundWorker Thread

Is there a way to immediately terminate a BackgroundWorke r thread? My
problem is that the BackgroundWorke r starts with a call to
My.Computer.Fil eSystem.GetFile s that can run for a very long time if
it is pointing to a directory tree with many files. If the user
requests cancellation during this time, the main thread can call
CancelAsync and can post a "Cancellati on Pending" message to the user,
but the BackgroundWorke r cannot respond to the CancellationPen ding
property until the call to My.Computer.Fil eSystem.GetFile s returns. It
seems inelegant to rewrite the call to My.Computer.Fil eSystem.GetFile s
to use calls to Dir or something that would allow me to poll the
CancellationPen ding property while I'm building the collection of file
names. And I have not wanted to rewrite the BackgroundWorke r as a
standard thread (read that "go through the learning curve"!). I would
rather abort the BackgroundWorke r thread but do not see how to do it.
>
Thanks.
>
redear

Is there a way to immediately terminate a BackgroundWorke r thread? My
problem is that the BackgroundWorke r starts with a call to
My.Computer.Fil eSystem.GetFile s that can run for a very long time if
it is pointing to a directory tree with many files. If the user
requests cancellation during this time, the main thread can call
CancelAsync and can post a "Cancellati on Pending" message to the user,
but the BackgroundWorke r cannot respond to the CancellationPen ding
property until the call to My.Computer.Fil eSystem.GetFile s returns.

>redear wrote:><snip>
>
>You may try using Thread.Abort, which will cause an exception to be
>thrown in the thread that you want to finish. You must call
>Thread.ResetAb ort in you Catch or Finally block, or else the exception
>will bubble up...
>
>A few words of caution, though: thread synchronization is almost an
>art, and maybe you start getting more troubles than the one you want
>to solve, such as bad breath, too much sugar in your coffee or strange
>calls to your cell phone at 3 a.m. ...
>
><code>
'At file level:
Imports SysThread = System.Threadin g
Imports SysComps = System.Componen tModel
>
'...
'At form level:
Private mThread As SysThread.Threa d
>
Private Sub BGWorker_DoWork ( _
ByVal Sender As Object, _
ByVal E As SysComps.DoWork EventArgs _
) Handles BGWorker.DoWork
>
mThread = SysThread.Threa d.CurrentThread
Try
For X As Integer = 0 To 100
SysThread.Threa d.Sleep(1000)
BGWorker.Report Progress(X)
Next
Catch Ex As SysThread.Threa dAbortException
SysThread.Threa d.ResetAbort()
End Try
End Sub
>
Private Sub BTNCancel_Click ( _
ByVal Sender As Object, _
ByVal E As System.EventArg s _
) Handles BTNCancel.Click
>
If BGWorker.IsBusy AndAlso _
mThread IsNot Nothing Then
mThread.Abort()
mThread = Nothing
End If
End Sub
></code>
>
>
>In the code above, BGWorker is the background worker component, and
>BTNCancel is, as you may have guessed, a "cancel" button.
>
>HTH.
>
>Regards,
>
>Branco.

Is there a way to immediately terminate a BackgroundWorke r thread? My
problem is that the BackgroundWorke r starts with a call to
My.Computer.Fil eSystem.GetFile s that can run for a very long time if
it is pointing to a directory tree with many files. If the user
requests cancellation during this time, the main thread can call
CancelAsync and can post a "Cancellati on Pending" message to the user,
but the BackgroundWorke r cannot respond to the CancellationPen ding
property until the call to My.Computer.Fil eSystem.GetFile s returns. It
seems inelegant to rewrite the call to My.Computer.Fil eSystem.GetFile s
to use calls to Dir or something that would allow me to poll the
CancellationPen ding property while I'm building the collection of file
names. And I have not wanted to rewrite the BackgroundWorke r as a
standard thread (read that "go through the learning curve"!). I would
rather abort the BackgroundWorke r thread but do not see how to do it.
>
Thanks.
>
redear

>I recommend you use FindFirstFile/FindNextFile/FindClose via
>pinvoke. That way you could periodically check for a pending
>cancel and then exit.
>
>For example, execute FindNextFile in a loop for 100 iterations,
>and then check for a pending cancel. If there is a pending cancel
>do a FindClose and exit the loop.
>
>-TP