VB.net 停止后台 worker

Question

我想创建一个按钮，可以停止我的后台工作人员并结束它正在处理的所有进程。

这是我的示例后台工作代码:

       Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

            Try
                If BackgroundWorker1.IsBusy <> True Then
                    BackgroundWorker1.RunWorkerAsync()
                End If
            Catch ex As Exception
            End Try

        End Sub

        Private Sub BackgroundWorker1_DoWork(sender As System.Object, e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork

            Dim counter As Integer = 1

            Do

            'updated code with stop function----------------
            BackgroundWorker1.WorkerSupportsCancellation = True
            If BackgroundWorker1.CancellationPending Then
                e.Cancel = True
                ProgressBar1.Value = 0
                Exit Do
            End If
            'updated code with stop function----------------

            ListBox1.Items.Add(counter)

            ProgressBar1.Value = ((counter - 1) / limit) * 100
            counter = counter + 1
            Loop While(counter <= 999999999999999999)

        End Sub

        Private Sub BackgroundWorker1_ProgressChanged(sender As System.Object, e As System.ComponentModel.ProgressChangedEventArgs) Handles BackgroundWorker1.ProgressChanged
            Try
            Catch ex As Exception
            End Try
        End Sub

        Private Sub BackgroundWorker1_Completed(sender As System.Object, e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
            Try
            Catch ex As Exception
            End Try
        End Sub

        Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
            System.Windows.Forms.Control.CheckForIllegalCrossThreadCalls = False    
        End Sub

        'updated code with stop function----------------
        Private Sub StopButton_Click(sender As Object, e As EventArgs) Handles StopButton.Click
              If BackgroundWorker1.IsBusy Then

                  If BackgroundWorker1.WorkerSupportsCancellation Then                
                     BackgroundWorker1.CancelAsync()
                  End If
              End If
        End Sub
        'updated code with stop function----------------

我想在停止后台工作时重置循环并将进度条返回到 0%。

这可能吗？

上面的代码已经更新，现在可以正常工作了。

我在 do 循环中添加了这段代码:

        BackgroundWorker1.WorkerSupportsCancellation = True
        If BackgroundWorker1.CancellationPending Then
            e.Cancel = True
            ProgressBar1.Value = 0
            Exit Do
        End If

我创建了一个停止工作人员的按钮:

    Private Sub StopButton_Click(sender As Object, e As EventArgs) Handles StopButton.Click
          If BackgroundWorker1.IsBusy Then

              If BackgroundWorker1.WorkerSupportsCancellation Then                
                 BackgroundWorker1.CancelAsync()
              End If
          End If
    End Sub

Answer 1

Backgroundworker 类具有方法 CancelAsync()您需要调用它来取消 bgw 的执行。

您需要设置 Backgroundworker.WorkerSupportsCancellation属性为 true 并且在 while 循环内您需要检查 CancellationPending属性值是否为 true表示调用 CancelAsync()方法。

如 CancellationPending评估为真，你会( 你应该已经做的 )调用重载的 ReportProgress() 之一( Docu ) 方法将您的 ProgressBar 值设置为所需的值。

编辑:您应该设置 Cancel DoWorkEventArgs 的属性(property)为 true 以便您可以检查 Cancelled RunWorkerCompletedEventArgs 的属性(property)内RunworkerCompleted事件。

您也不应该访问位于 UI 线程中的任何控件。你最好使用 ProgressChanged ( Docu ) 事件。

见:BackgroundWorker Docu