Question

我需要运行一个报告来获取学生测试的摘要，该摘要显示已通过或未通过详细信息。单击cmd_Start时，它在Backgroundworker上运行（我只想以多线程运行，我发现人们建议使用backgroundworker）为每个学生运行，并在完成所有计算后弹出一个带有结果的消息框。我在其他示例中复制并编辑了一些代码，但我不知道应该在我标记问号的代码上添加什么。其他想法也很受欢迎。

  Dim Passed as int32= 0
  Dim Failed as int32 = 0
  Dim Total as int32 = 0

  Private Sub cmd_Start_Click(sender As Object, e As EventArgs) Handles cmd_Start.Click
    Passed= 0
    Failed = 0
    Total = 0
    For i as int32 = 0 to ubound(StudentIDAry)
        Dim worker As New System.ComponentModel.BackgroundWorker
        AddHandler worker.DoWork, ????? CountAverageScore(????,????, StudentIDAry(i))
        AddHandler worker.RunWorkerCompleted, AddressOf HandleThreadCompletion
        worker.RunWorkerAsync()
    Next
    MsgBox("Total Counted: " & Total & vbcrlf & "Passed Count: " & Passed & vbcrlf & "Failed Count: " & Failed)
  End Sub

  Private Sub CountAverageScore(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs, ByVal StudentID As Long)
     Dim stroutput As String = e.Argument.ToString
     ..........
     ..........
     e.Result = stroutput
  End Sub

  Private Sub HandleThreadCompletion(ByVal sender As Object, ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs)
    Dim return_value As String = e.Result.ToString
    If cint(return_value)>=50 Then
        Passed = Passed + 1
    Else
        Failed = Failed + 1
    End If
    Total = Total + 1
 End Sub

Answer 1

不要使用添加自己的后台工作程序的所有代码，请尝试此操作。它使用Parallel.For并在其自己的线程中运行循环内的所有内容。

Parallel.For的结构非常简单，但重要的是要记住表示循环最后一次迭代的数字是独占的。

例如，在常规循环For I As Integer =0 to 100中，将为100，但在Parallel.For循环中，最后一次迭代将为99.令人讨厌，但这是怎么回事。

由于多线程的性能开销，您的代码可能无法运行得更快，并且与常规循环相比，可能值得检查它在并行循环中的运行速度。

别忘了改变我使用StudentStruct的代码，将其用于代表个别学生的任何对象。

Private Sub cmd_Start_Click(sender As Object, e As EventArgs) Handles cmd_Start.Click
    Passed = 0
    Failed = 0
    Total = 0
            Parallel.For(0, UBound(StudentIDAry) + 1,
                                      Sub(index As Integer)
                                          Dim studentAverage As Integer = CInt(CountAverageScore(StudentIDAry(index)))
                                          If CInt(studentAverage) >= 50 Then
                                              Passed = Passed + 1
                                          Else
                                              Failed = Failed + 1
                                          End If
                                          Total = Total + 1
                                      End Sub)
    MsgBox("Total Counted: " & Total & vbCrLf & "Passed Count: " & Passed & vbCrLf & "Failed Count: " & Failed)
End Sub


Private Function CountAverageScore(student As StudentStruct) As Single
    Dim score As Integer
    '
    '
    '
    Return score
End Function

抛弃所有BackgroundWorker代码，只使用上面的

VB.net Backgroundworker传递参数和返回值

1 个答案: