VB.Net Backgroudworker

Question

我使用Visual Studio 2013进行Visual Basic，我正在努力调试我的多线程程序。

我正在使用一个背景工作者，它似乎与我认为应该如何有所不同。

我不明白为什么我的程序仅处理我的Arraylist中的第一个条目叫arFileName。

For Each在BackgroundWorker1.Dowork过程中的语句在以下代码中未能通过整个arFileName迭代：

Private Sub btnRun_Click(sender As Object, e As EventArgs) Handles btnSelectCsv.Click
    'arFileName is ArrayList and it has enormous counts
    ProgressBar1.Maximum = arFileName.Count
    Me.Cursor = Cursors.WaitCursor
    'Do background
    BackgroundWorker1.RunWorkerAsync()
    Me.Cursor = Cursors.Arrow
    MessageBox.Show("Finished!", "info", MessageBoxButtons.OK, MessageBoxIcon.Asterisk)

End Sub

Private Sub BackgroundWorker1_DoWork(sender As Object, e As System.ComponentModel.DoWorkEventArgs) _
    Handles BackgroundWorker1.DoWork
    Dim arNotFoundFile As New ArrayList
    'Confirm file exists
    For Each filename As String In arFileName ' Here!
        If Not IO.File.Exists(filename) Then
            arNotFoundFile.Add(filename)
            ProgressBar1.Value = ProgressBar1.Value + 1
        End If
    Next
End Sub

Answer 1

必须设置后台工作者以报告其进度

 BackgroundWorker1.WorkerReportsProgress = True

那么，典型的实现可能如下：

Dim progress As Integer = 0
Private Sub BackgroundWorker1_DoWork(sender As Object, e As DoWorkEventArgs) Handles BackgroundWorker1.DoWork
    While (progress < 100)
        ' YOUR CODE HERE
        progress += 1
        BackgroundWorker1.ReportProgress(progress)
    End While
End Sub
Private Sub BackgroundWorker1_ProgressChanged(sender As Object, e As ProgressChangedEventArgs) Handles BackgroundWorker1.ProgressChanged
    ' YOUR PROGRESSBAR VALUE HERE, USING progress VARIABLE
End Sub
Private Sub BackgroundWorker1_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
    MessageBox.Show("Work completed")
End Sub
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    BackgroundWorker1.WorkerReportsProgress = True
    BackgroundWorker1.RunWorkerAsync()
End Sub

您可以看到，我已经定义了 progress 变量，这将跟踪完成的工作百分比。在我们使用 runworkerAsync form_load 事件中启动背景工作者（我将其进行到 form_load 事件）之后，我们可以通过 progressChangedChanged 事件来跟踪其进度：在这里，我们使用了由我们的工作修改的进度变量（ dowork ）。您可以使用它来设置progressbar值属性。最后，完成所有操作后，我们将消息发射到适当的事件中，即 runworkercompleted