vb.net - 后台 worker 和 SaveDialog

Question

我对后台工作人员控制非常陌生。我有一个构建文件的现有项目，但在整个项目中构建文件时出现死锁错误。我试图通过创建另一个仅由后台工作人员组成的项目来解决这个问题。然后我将合并它们。

我的问题是我不知道在哪里实现我的后台工作人员会更有效，而且主要问题是如何将 SaveDialog 与我的后台工作人员一起使用？我需要向我的后台工作项目发送一个参数，告诉它何时构建我的文件以及何时完成。

这是构建我的文件的位置:

  srOutputFile = New System.IO.StreamWriter(strFile, False) 'Create File

  For iSeqNo = 0 To iPrintSeqNo
    ' Loop through al the record types
    For Each oRecord As stFileRecord In pFileFormat
      If dsFile.Tables.Contains(oRecord.strRecordName) Then
        ' Loop through al the records
        For Each row As DataRow In dsFile.Tables(oRecord.strRecordName).Rows
          ' Check record id
          If oRecord.strRecordId.Length = 0 Then
            bMatched = True
          Else
            bMatched = (CInt(oRecord.strRecordId) = CInt(row.Item(1)))
          End If

          ' Match records
          If iSeqNo = CInt(row.Item(0)) And bMatched Then
            strRecord = ""
            ' Loop through al the fields
            For iLoop = 0 To UBound(oRecord.stField)
              ' Format field
              If oRecord.stField(iLoop).iFieldLength = -1 Then
                If strRecord.Length = 0 Then
                  strTmp = row.Item(iLoop + 1).ToString
                Else
                  strTmp = strDelimiter & row.Item(iLoop + 1).ToString
                End If
              ElseIf oRecord.stField(iLoop).eFieldType = enumFieldType.TYPE_VALUE Or _
                     oRecord.stField(iLoop).eFieldType = enumFieldType.TYPE_AMOUNT_CENT Then

                strTmp = row.Item(iLoop + 1).ToString.Replace(".", "").PadLeft(oRecord.stField(iLoop).iFieldLength, "0")
                strTmp = strTmp.Substring(strTmp.Length - oRecord.stField(iLoop).iFieldLength)
              Else
                strTmp = row.Item(iLoop + 1).ToString.PadRight(oRecord.stField(iLoop).iFieldLength, " ").Substring(0, oRecord.stField(iLoop).iFieldLength)
              End If

              If oRecord.stField(iLoop).iFieldLength > -1 And (bForceDelimiter) And strRecord.Length > 0 Then
                strTmp = strDelimiter & strTmp
              End If

              strRecord = strRecord & strTmp
            Next

            ' Final delimiter
            If (bForceDelimiter) Then
              strRecord = strRecord & strDelimiter
            End If

            srOutputFile.WriteLine(strRecord)
          End If
        Next
      End If
    Next
  Next

Answer 1

你可以试试这个:

Private locker1 As ManualResetEvent = New System.Threading.ManualResetEvent(False)
Private locker2 As ManualResetEvent = New System.Threading.ManualResetEvent(False)
Dim bOpenFileOK As Boolean
Dim myOpenFile As OpenFileDialog = New OpenFileDialog()

Private Sub FileOpener()
    While Not bTerminado
        If myOpenFile.ShowDialog() = System.Windows.Forms.DialogResult.OK Then
            bOpenFileOK = True
        Else
            bOpenFileOK = False
        End If

        locker2.Set()
        locker1.WaitOne()
    End While
End Sub

' Detonator of the action
Private Sub Button1_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles Button1.Click
    Dim tFileOp As Thread = New Thread(AddressOf FileOpener)
    tFileOp.SetApartmentState(ApartmentState.STA)
    tFileOp.Start()

    ' Start BackgroundWorker
    BW1.RunWorkerAsync()
End Sub

Private Sub AsyncFunctionForBW(ByVal args As ArrayList)
    '[...]

    'Change options dinamically for the OpenFileDialog
    myOpenFile.Filter = ""
    myOpenFile.MultiSelect = True

    'Calling the FileDialog
    locker1.Set()
    locker2.WaitOne()
    locker1.Reset()
    locker2.Reset()

    If bOpenFileOK Then
        myStream = myOpenFile.OpenFile()

        '[...]
    End If
End Sub

虽然有点复杂，但是很有效。

ManualResetEvents 会在到达时中断代码的执行(如果它们被告知停止)，直到您使用 .Set()。如果您使用.WaitOne()，则将其设置为停止模式，因此到达时它将再次停止。

此代码定义了两个ManualResetEvents。当您单击 Button1 时，会在新的 Thread 中启动函数 FileOpener()，然后启动 BackgroundWorker。 FileOpener() 函数显示一个 FileOpenDialog 并在 locker1 中等待，因此当您使用 locker1.Set() 时该函数显示文件对话框。

由于myOpenFile是一个“全局”变量(以及bOpenFileOK)，一旦用户选择(或不选择)文件，您就可以检测对话框结果( bOpenFileOK) 和选定的文件。