BackgroundWorker的发件人错了

Question

我实现了这样的进度条：

TableCreation.ProgressBar2.Value = 0
TableCreation.ProgressBar2.Maximum = CInt(FieldsNumber)
'==================
For SecondLoopCount = 1 To CInt(FieldsNumber) Step 1
    '----------------------------------------------
    TableCreation.ProgressBar2.Value = SecondLoopCount
    TableCreation.ProgressBar2.Refresh()
    TableCreation.ProgressBar2.Show()
    ' ....... Some Code ......
Next

我在此子句中处理BackgroundWorker的{​​{1}}事件：

DoWork

但是当我这样做时：

Public Shared Sub bw_DoWork(ByVal sender As Object, ByVal e As DoWorkEventArgs)
    Dim bw As BackgroundWorker = New BackgroundWorker
    Dim worker As BackgroundWorker = CType(sender, BackgroundWorker)
    For i = 1 To 10
        If worker.CancellationPending = True Then
            e.Cancel = True
            Exit For
        Else
            ' Perform a time consuming operation and report progress.
            System.Threading.Thread.Sleep(500)
            worker.ReportProgress(i * 10)
        End If
    Next
End Sub

如果Dim e1 As System.ComponentModel.DoWorkEventArgs TableCreation.ProgressBar2.Value = SecondLoopCount TableCreation.ProgressBar2.Refresh() TableCreation.ProgressBar2.Show() bw_DoWork(sender, e1) 是一个Object，则会抛出错误：

  

无法将类型为'e_s​​tore.TableCreation'的对象强制转换为'System.ComponentModel.BackgroundWorker'。

sender只是我项目中的一个表单。

Answer 1

您不应该直接致电bw_DoWork()。这就是错误发生的地方，您在当前上下文（表单）中发送sender对象，然后尝试将其转换为BackgroundWorker。

您应该将处理程序添加到DoWork Sub，

Public Shared Sub bw_DoWork(ByVal sender As Object, ByVal e As DoWorkEventArgs) Handles bw.DoWork

然后，不要直接致电bw_DoWork()，而是bw.RunWorkerAsync()。然后，这将引发DoWork事件并调用该方法。然后，您的sender将成为BackgroundWorker。