Stop a background worker - vb.net

Question

I am trying to add a STOP button to my program to, stop a background worker. I have had no luck doing it with the following.
This is my button event
Private Sub GOButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles GOButton.Click
If BackgroundWorker1.IsBusy Then
Exit Sub
Else
PullIPs()
End If
End If
End Sub
The PullIPs sub does alot of stuff, and at the end, starts the backgroundworker
BackgroundWorker1.RunWorkerAsync()
Backgroundworker1 kicks off another sub, like so
Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
BackgroundWorker1.ReportProgress(50)
PingAll()
End Sub
So, after that maze, I would like a way to stop the backgroundworker mid 'PingAll()'.
Lastly,
Private Sub StopButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles StopButton.Click
BackgroundWorker1.CancelAsync()
End Sub
Note: SupportCancelation IS enabled. I have also looked all over the place, and it looks like I am doing it, how it should work...

Answer 1

It appears that you have looked all over the place except for the one obvious place that you should have looked first, i.e. the Help documentation. The doco for the BackgroundWorker.CancelAsync method has this to say:
CancelAsync submits a request to terminate the pending background
operation and sets the CancellationPending property to true.
When you call CancelAsync, your worker method has an opportunity to
stop its execution and exit. The worker code should periodically check
the CancellationPending property to see if it has been set to true.
Where in your code are you doing as that instructs? Nowhere, so you're obviously not doing it how it should work.
Calling CancelAsync only requests a cancellation. It's still up to you to add code to your DoWork event handler to test whether a cancellation has been requested and stop doing the work if it has. The DoWork event handler can do anything at all so calling CancelAsync is not going to simply abort that on the spot without any consideration for what state the app is in and whether any cleanup may be required.
You know what work is being done so it's up to you write the code such that that work can be cancelled part way through. As it is, all you're doing is a single call to PingAll so there is no way to cancel it. You need to restructure that code, e.g. turn it into a loop that does one ping per iteration and then you can cancel between iterations if required.