WPF

Imports Microsoft.VisualBasic
Imports System
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Text
Imports System.Threading
Imports System.Windows
Imports System.Windows.Controls
Imports System.Windows.Data
Imports System.Windows.Documents
Imports System.Windows.Input
Imports System.Windows.Media
Imports System.Windows.Media.Imaging
Imports System.Windows.Shapes


Namespace WindowsApplication1
	

	Partial Public Class Window1
		Inherits System.Windows.Window
        Private WithEvents _worker As BackgroundWorker
		Public Sub New()
			InitializeComponent()
		End Sub

		Private Sub StartWorker(ByVal sender As Object, ByVal e As RoutedEventArgs)

		End Sub

        

		Private Sub button1_Click(ByVal sender As Object, ByVal e As RoutedEventArgs)
            _worker = New BackgroundWorker()
			_worker.WorkerReportsProgress = True
			_worker.WorkerSupportsCancellation = True

            AddHandler _worker.DoWork, AddressOf DoWorkEventHandler


            AddHandler _worker.ProgressChanged, AddressOf ProgressChangedEventHandler
            AddHandler _worker.RunWorkerCompleted, AddressOf RunWorkerCompletedEventHandler
			_worker.RunWorkerAsync()
			_btnStart.IsEnabled = False
			_btnCancel.IsEnabled = True
		End Sub
		
		
        Private Sub DoWorkEventHandler(ByVal s As Object, ByVal args As DoWorkEventArgs) Handles _worker.DoWork
            Dim worker As BackgroundWorker = TryCast(s, BackgroundWorker)
            For i As Integer = 0 To 4
                If worker.CancellationPending Then
                    args.Cancel = True
                    Return
                End If
                Thread.Sleep(100)
                worker.ReportProgress(i + 1)
            Next i
        End Sub
		
        Private Sub ProgressChangedEventHandler(ByVal s As Object, ByVal args As ProgressChangedEventArgs) Handles _worker.ProgressChanged
            _progressBar.Value = args.ProgressPercentage

        End Sub
		
        Private Sub RunWorkerCompletedEventHandler(ByVal s As Object, ByVal args As RunWorkerCompletedEventArgs) Handles _worker.RunWorkerCompleted
            _btnStart.IsEnabled = True
            _btnCancel.IsEnabled = False
            _progressBar.Value = 0

        End Sub
        Private Sub CancelWorker(ByVal sender As Object, ByVal e As RoutedEventArgs)
            _worker.CancelAsync()
        End Sub
	End Class
End Namespace