Public Class clsThreadTest
 
    Private WithEvents WORKER As New System.ComponentModel.BackgroundWorker
 
    Public Event NewINfo(ByVal InfoNr As Integer, ByVal InfoText As String)
 
    Public Sub StartScan()
        Me.WORKER.WorkerReportsProgress = True
        Me.WORKER.WorkerSupportsCancellation = True
        Me.WORKER.RunWorkerAsync()
    End Sub
 
    Public Sub CancelScan()
        If Me.WORKER.IsBusy Then
            Me.WORKER.CancelAsync()
        End If
    End Sub
 
    Private Sub worker_DoWork(ByVal sender As Object, ByVal e As _
      System.ComponentModel.DoWorkEventArgs) Handles WORKER.DoWork
 
        Dim I As Long
        Dim j As Long
 
        WORKER.ReportProgress(3, Now & " - " & "START")
 
        For I = 1 To 100
 
            WORKER.ReportProgress(0, I & "%")
 
            Dim PI As Double = 0
            For j = 1 To 400
                PI = 0
                For ii As Integer = 0 To 100
                    PI += 1 / Math.Pow(16, ii) * (4 / ((8 * ii) + 1) - 2 / ((8 _
                      * ii) + 4) - 1 / ((8 * ii) + 5) - 1 / ((8 * ii) + 6))
                Next
 
                WORKER.ReportProgress(1, j & " - Pi: " & PI)
            Next
 
            If WORKER.CancellationPending = True Then Exit For
 
        Next
 
        WORKER.ReportProgress(3, Now & " - " & "ENDE")
 
    End Sub
 
    Private Sub worker_ProgressChanged(ByVal sender As Object, ByVal e As _
      System.ComponentModel.ProgressChangedEventArgs) Handles _
      WORKER.ProgressChanged
        RaiseEvent NewINfo(e.ProgressPercentage, e.UserState)
    End Sub
 
End Class

Public Class frmTestKlasse
 
    Private WithEvents Scan1 As New clsThreadTest
 
    Private Sub butStart_Click(sender As System.Object, e As System.EventArgs) _
      Handles butStart.Click
        Call StartScanning()
    End Sub
 
    Private Sub butCancel_Click(sender As System.Object, e As System.EventArgs) _
      Handles butCancel.Click
        Scan1.CancelScan()
    End Sub
 
    Private Sub StartScanning()
        Scan1 = New clsThreadTest
        Scan1.StartScan()
    End Sub
 
    Private Sub Scan1_NewINfo(InfoNr As Integer, InfoText As String) Handles _
      Scan1.NewINfo
        Select Case InfoNr
            Case 0
                lbInfo_Loop1.Text = InfoText
            Case 1
                lbInfo_Loop2.Text = InfoText
            Case 3
                rtbLog.AppendText(InfoText & vbCrLf)
        End Select
        'Debug.Print(Now & " - " & InfoText)
    End Sub
 
End Class