下面是一些示例code，引导您完成：

Here is some sample code to guide you through:

Public Class Form1

    Public WithEvents bgwWorker1 As System.ComponentModel.BackgroundWorker

    Public Sub New()

        ' This call is required by the designer.
        InitializeComponent()

        ' Add any initialization after the InitializeComponent() call.
        bgwWorker1 = New System.ComponentModel.BackgroundWorker
        With bgwWorker1
            .WorkerReportsProgress = True       'we'll need to report progress
            .WorkerSupportsCancellation = True  'allows the user to stop the activity
        End With

    End Sub

    Private Sub Form1_Disposed() Handles Me.Disposed
        'you'll need to dispose the backgroundworker when the form closes.
        bgwWorker1.Dispose()
    End Sub

    Private Sub btnStart_Click() Handles btnStart.Click
        'check if the backgroundworker is doing something
        Dim waitCount = 0

        'wait 5 seconds for the background worker to be free
        Do While bgwWorker1.IsBusy AndAlso waitCount <= 5
            bgwWorker1.CancelAsync()     'tell the backgroundworker to stop
            Threading.Thread.Sleep(1000) 'wait for 1 second
            waitCount += 1
        Loop

        'ensure the worker has stopped else the code will fail
        If bgwWorker1.IsBusy Then
            MsgBox("The background worker could not be cancelled.")
        Else
            If optStep2.Checked Then
                bgwWorker1.RunWorkerAsync(2)
            ElseIf optStep3.Checked Then
                bgwWorker1.RunWorkerAsync(3)
            End If
            btnStart.Enabled = False
            btnStop.Enabled = True
        End If
    End Sub

    Private Sub btnStop_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnStop.Click
        'to stop the worker, send the cancel message
        bgwWorker1.CancelAsync()
    End Sub

    Private Sub bgwWorker1_DoWork(ByVal sender As Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles bgwWorker1.DoWork
        'get the value to be used in performing the steps
        'in your case, you might have to convert it to a string or something 
        'and then do a Select Case on the result.
        Dim stepValue = CInt(e.Argument)

        'you cannot change the property of any control from a thread different
        'from the one that created it (the UI Thread) so this code would fail.
        'txtResults.Text &= "Starting count in steps of " & stepValue & vbCrLf

        'to perform a thread-safe activity, use the ReportProgress method like so
        bgwWorker1.ReportProgress(0, "Reported: Starting count in steps of " & stepValue & vbCrLf)

        'or invoke it through an anonymous or named method
        Me.Invoke(Sub() txtResults.Text &= "Invoked (anon): Starting count in steps of " & stepValue & vbCrLf)
        SetTextSafely("Invoked (named): Starting count in steps of " & stepValue & vbCrLf)

        For i = 0 To 1000 Step stepValue
            'Visual Studio Warns: Using the iteration variable in a lambda expression may have unexpected results.  
            '                     Instead, create a local variable within the loop and assign it the value of 
            '                     the iteration variable.
            Dim safeValue = i.ToString
            Me.Invoke(Sub() txtResults.Text &= safeValue & vbCrLf)

            'delibrately slow the thread
            Threading.Thread.Sleep(300)

            'check if there is a canellation pending
            If bgwWorker1.CancellationPending Then
                e.Cancel = True 'set this to true so we will know the activities were cancelled
                Exit Sub
            End If
        Next
    End Sub

    Private Sub SetTextSafely(ByVal text As String)
        If Me.InvokeRequired Then
            Me.Invoke(Sub() SetTextSafely(text))
        Else
            txtResults.Text &= text
        End If
    End Sub

    Private Sub bgwWorker1_ProgressChanged(ByVal sender As Object, ByVal e As System.ComponentModel.ProgressChangedEventArgs) Handles bgwWorker1.ProgressChanged
        'everything done in this event handler is on the UI thread so it is thread safe
        txtResults.Text &= e.UserState.ToString
    End Sub

    Private Sub bgwWorker1_RunWorkerCompleted(ByVal sender As Object, ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles bgwWorker1.RunWorkerCompleted
        'everything done in this event handler is on the UI thread so it is thread safe
        If Not e.Cancelled Then
            txtResults.Text &= "Activities have been completed."
        Else
            txtResults.Text &= "Activities were cancelled."
        End If

        btnStart.Enabled = True
        btnStop.Enabled = False
    End Sub

    Private Sub txtResults_TextChanged() Handles txtResults.TextChanged
        'place the caret at the end of the line and then scroll to it
        'so that we always see what is happening.
        txtResults.SelectionStart = txtResults.TextLength
        txtResults.ScrollToCaret()
    End Sub
End Class

这是与它去的形式：

And this is the form that goes with it:

另外还要考虑读MSDN上的以下文章：

Also consider reading the following articles on MSDN:

在code以上的VB 10件作品（VS 2010）只。为了实现相同的code在其他版本的VB，你必须写一个显著金额code，因为它们不支持匿名委托。

The code above works in VB 10 (VS 2010) only. In order to implement the same code in other versions of VB, you'll have to write a significant amount of code as they do not support anonymous delegates.

在旧版本的VB，行

Public Sub Sample()
    Me.Invoke(Sub() txtResults.Text &= safeValue & vbCrLf)
End Sub

转换为这样的事情：

translates to something like this:

Public Delegate AnonymousMethodDelegate(value as String)

Public Sub AnonymousMethod(value as String)
    txtResults.Text &= value
End Sub

Public Sub Sample()
    Me.Invoke(New AnonymousMethodDelegate(AddressOf AnonymousMethod), safeValue & vbCrLf)
End Sub

按照以下步骤获得code $ p中$ P VB工作10

Follow these steps to get the code to work in pre VB 10

添加此委托

Delegate Sub SetTextSafelyDelegate(ByVal text As String)

，然后更改所有 Me.Invoke（子（）SetTextSafely（文本））到

Me.Invoke(New SetTextSafelyDelegate(AddressOf SetTextSafely), text)

另外请注意，任何地方，我设置一个匿名委托的文字，你就必须重写code调用 SetTextSafely 方法。

例如，行 Me.Invoke（子（）txtResults.Text和放大器; = safeValue和放大器; vbCrLf）中的for循环部分的 bgwWorker_DoWork 将成为 SetTextSafely（safeValue和放大器; vbCrLf）

For instance, the line Me.Invoke(Sub() txtResults.Text &= safeValue & vbCrLf) in the for loop section of the bgwWorker_DoWork will become SetTextSafely(safeValue & vbCrLf)

如果您想了解更多有关代表，阅读下面的文章（均来自MSDN）

If you'd like to know more about delegates, read the following articles (all from MSDN)