Public Class Form1
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MyBase.Load
        BackgroundWorker1.WorkerSupportsCancellation = True
        BackgroundWorker1.RunWorkerAsync()
    End Sub
 
    Private Sub BackgroundWorker1_DoWork(ByVal sender As Object, ByVal e As _
      System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
        For i As Integer = 0 To 9
            System.Threading.Thread.Sleep(1000)
            If BackgroundWorker1.CancellationPending Then
                e.Cancel = True
                Exit Sub
            End If
        Next
    End Sub
 
    Private Sub BackgroundWorker1_RunWorkerCompleted(ByVal sender As Object, _
      ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles _
      BackgroundWorker1.RunWorkerCompleted
        If e.Cancelled Then
            MsgBox("cancel")
        Else
            MsgBox("complete")
        End If
    End Sub
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        If BackgroundWorker1.IsBusy Then
            BackgroundWorker1.CancelAsync()
        End If
    End Sub
End Class