VB.net 继续

Question

我有这段代码循环遍历列表中的所有帐户，然后使用每个帐户的任务对帐户执行某些操作以加快流程。每次程序完成此操作时，我都希望用户界面更新进度条。我以前使用过 Invoke，但它不是最佳选择，而且我无法使其正常工作。现在我知道这可以使用后台工作者来完成，但这不是使您的应用程序多线程化的最佳方式，所以我使用了它。我没有调用，而是听说了 ContinueWith，但我似乎无法让它工作，而且我没有收到任何错误消息，只是一条红色下划线。代码：

progressBar.Value = 0
    Dim tasks As New List(Of Task)()
    For Each account In combos
        Dim t As Task = Task.Run(Sub()
                                     While checked = False
                                         If proxies.Count = 0 Then
                                             Exit Sub
                                             'Also can't think of a good way to stop searching through accounts when there are no proxies left in my queue.
                                         End If
                                         Dim proxy As New WebProxy(proxies(0))
                                         proxies.TryDequeue(0)
                                         'Do something
                                     End While
                                     checkedAmount += 1
                                     Dim progress As Integer = ((checkedAmount / combos.Count) * 100)
                                     Task.ContinueWith(progressBar.Value = progress, TaskScheduler.FromCurrentSynchronizationContext()) 'Error here
                                 End Sub)
        tasks.Add(t)
    Next
    Task.WaitAll(tasks.ToArray())

我没有收到错误代码，如下所示：

我也试过在后面放一个潜艇之类的东西，但那什么也没有。提前感谢您的帮助。

尝试调用更新：

 Private Delegate Sub UpdateProgressBarDelegate(ByVal progressBarUpdate As ProgressBar, ByVal value As Integer)

Dim checkedAmount As Integer = 0
Dim checked As Boolean = False
Private Sub startBtn_Click(sender As Object, e As EventArgs) Handles startBtn.Click
    progressBar.Value = 0
    Dim tasks As New List(Of Task)()
    For Each account In combos
        Dim t As Task = Task.Run(Sub()
                                     While checked = False
                                         proxies.TryDequeue(0)
                                         'do stuff
                                     End While
                                     checkedAmount += 1
                                     Dim progress As Integer = ((checkedAmount / combos.Count) * 100)
                                     If Me.InvokeRequired = True Then
                                         Me.Invoke(New UpdateProgressBarDelegate(AddressOf UpdateProgressBar), progressBar, progress)
                                     Else
                                         UpdateProgressBar(progressBar, progress)
                                     End If
                                     'Task.ContinueWith(progressBar.Value = progress, TaskScheduler.FromCurrentSynchronizationContext())
                                 End Sub)
        tasks.Add(t)
    Next
    Task.WaitAll(tasks.ToArray())
End Sub

Private Sub UpdateProgressBar(ByVal ProgressBarUpdate As ProgressBar, progress As Integer)
    progressBar.Value = progress
End Sub

仍然不起作用不知道为什么？

Answer 1

Now I know this can be done using a background worker but this isn't the best way of making your application multithreaded

有点。

BackgroundWorker 是单独运行许多不同任务的糟糕方法。没有人愿意为每个任务处理一个单独的 BackgroundWorker 组件。但是 one BackgroundWorker 是一种 很棒的 方法，它只产生一个额外的线程来管理所有其他任务并更新进度条。这是一个简单的解决方案。

无论哪种方式，您肯定要做的一件事是移动代码以更新单个任务中的 ProgressBar。将它放在任务中违反了关注点分离¹。执行此操作后，您还需要更改对 WaitAll() 的调用以在知道您有多少任务的循环中使用 WaitAny()，这样您仍然可以在每个任务完成时更新 ProgressBar。这也可能会产生解决您当前问题的副作用。

Private Async Sub startBtn_Click(sender As Object, e As EventArgs) Handles startBtn.Click

    Dim tasks As New List(Of Task)()
    For Each account In combos
       Dim t As Task = Task.Run(Sub()
                                 While Not checked
                                     proxies.TryDequeue(0)
                                     'do stuff
                                 End While
                               End Sub)
        tasks.Add(t)
    Next


    progressBar.Value = 0
    For i As Integer = 1 To tasks.Count 
        Dim t = Await Task.WhenAny(tasks) 
        tasks.Remove(t)
        progressBar.Value  = (i / combos.Count) * 100
    Next i
End Sub

_{1 这里的问题说明了我们关心关注点分离的一个原因。一旦我解决了这个问题，代码就会变得简单得多并且令人沮丧的错误就会消失。}

VB.net 继续

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