后台工作者取消异步无效

Question

程序逻辑

我正在运行一名后台工作人员来读写文件。为了检查是否单击了取消按钮，我创建了一个名为“ check_bgWorkerCancelled（）”的方法，该方法应该在取消挂起时处理所有事件。

问题

当我单击取消按钮时，工作人员继续运行。当我单击开始按钮时，旧进程继续运行。

代码：用于检查取消

' Method: To check is cancellation is pending
    Private Sub check_bgWorkerCancelled()
        ' check if cancellation is pending
        If bgWorker_Scanner.CancellationPending = True Then
            ' background worker cancel asynchronous operating
            If bgWorker_Scanner.IsBusy Then
                Try 'try to
                    ' cancel the threads
                    bgWorker_Scanner.CancelAsync()
                    ' dispose the background worker
                    bgWorker_Scanner.Dispose()
                Catch ex As Exception 'if exception
                    ' invoke error
                    utils.invoke_msg(3, "Worker Error", ex.Message.ToString)
                    Me.Close() 'close form
                End Try
            End If
            isScanning = False 'set scanning to false
            Try
                ' invoke to bypass illegal cross threading UI update
                BeginInvoke(CType(Sub()
                                      progressBar1.Value = 0
                                      txtStatus.Text = "Cancelled"
                                      txtCalmDown.Text = ""
                                      btnToggleScan.Image = Image.FromFile(Application.StartupPath & "/res/malware_scanner/rocket.png")
                                  End Sub, MethodInvoker))
            Catch ex As Exception : End Try
        Else
            Exit Sub
        End If
    End Sub

尝试过的解决方案

我尝试了以下解决方案，但没有一个起作用：

试图检查DoWork事件中是否已取消

Private Sub bgWorker_Scanner_DoWork(sender As Object, e As System.ComponentModel.DoWorkEventArgs) Handles bgWorker_Scanner.DoWork
    If bgWorker_Scanner.CancellationPending = True Then
        e.CancelAsync()
        bgWorker_Scanner.dispose()
    End If
End Sub

试图检查取消并收集垃圾

Private Sub bgWorker_Scanner_DoWork(sender As Object, e As System.ComponentModel.DoWorkEventArgs) Handles bgWorker_Scanner.DoWork
    If bgWorker_Scanner.CancellationPending = True Then
        e.CancelAsync()
        bgWorker_Scanner.dispose()
        GC.Collect()
    End If
End Sub

试图在Try-Catch语句中执行上述操作

Private Sub bgWorker_Scanner_DoWork(sender As Object, e As System.ComponentModel.DoWorkEventArgs) Handles bgWorker_Scanner.DoWork
    If bgWorker_Scanner.CancellationPending = True Then
        If bgWorker_Scanner.IsBusy Then
            Try
                e.CancelAsync()
                bgWorker_Scanner.dispose()
                GC.Collect()
            Catch ex As Exception
                MsgBox(ex.Message.ToString)
        End If
    End If
End Sub

有什么方法可以结束后台工作，而不必完全关闭表单？任何帮助表示赞赏。