VB.net停止后台工作 [英] VB.net stopping a backgroundworker
问题描述
我想创建一个按钮，该按钮可以停止后台工作人员并结束其正在执行的所有过程.
这是我的示例背景工作人员代码:
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----------------
我想重置循环，并在我停止后台工作人员时将进度栏恢复为0％.
这可能吗?
上面的代码已更新，现在可以正常工作.
我已将此代码添加到我的do循环中:
BackgroundWorker1.WorkerSupportsCancellation = True
If BackgroundWorker1.CancellationPending Then
e.Cancel = True
ProgressBar1.Value = 0
Exit Do
End If
我创建了一个按钮来停止工作进程:
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
Backgroundworker类具有方法CancelAsync()，您需要调用该方法来取消bgw的执行.
您需要将Backgroundworker.WorkerSupportsCancellation属性设置为true，并在while循环内需要检查CancellationPending属性，如果该值是true，则表示已调用CancelAsync()方法.
如果CancellationPending评估为true，则您将(您应该已经完成的操作)调用重载的ReportProgress()之一( Docu )事件.
请参阅: BackgroundWorker文档
I want to create a button that could stop my background worker and end all the process it is working on.
Here is my sample backgroundworker code:
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----------------
I want to reset the loop and return the Progress Bar to 0% when i stop the backgroundworker.
Is this possible?
The code above has been updated and it is now working fine.
I have added this code inside my do loop:
BackgroundWorker1.WorkerSupportsCancellation = True
If BackgroundWorker1.CancellationPending Then
e.Cancel = True
ProgressBar1.Value = 0
Exit Do
End If
I created a button that stops the worker:
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
The Backgroundworker class has the method CancelAsync() which you need to call to cancel the execution of the bgw.
You need to set the Backgroundworker.WorkerSupportsCancellation property to true and inside the while loop you need to check the CancellationPending property wether the value is true which indicates a call to the CancelAsync() method.
If CancellationPending evaluates to true, you would ( which you should have done already ) call one of the overloaded ReportProgress() (Docu) methods to set your ProgressBar value to the desired value.
EDIT: You should set the Cancel property of the DoWorkEventArgs to true so you can check the Cancelled property of the RunWorkerCompletedEventArgs inside the RunworkerCompletedevent.
You also shouldn not access any controls which lives in the UI thread. You better use the ProgressChanged(Docu) event.
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