Question

我只想在后台工作时更改文本框文本。我所拥有的是：

Private Sub ...

 Dim powershellWorker As New BackgroundWorker
        AddHandler powershellWorker.DoWork, AddressOf BackgroundWorker1_DoWork

        powershellWorker.RunWorkerAsync()

End Sub

Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork

 If stuff <> "lol" Then
            test.Text = stuff

End Sub

它给了我错误：＆＃34;无效的线程 - 边界操作＆＃34; （谷歌翻译）

Answer 1

您无法从创建控件的线程以外的线程更改大多数控件属性。

检查是否需要调用，即当前代码是在创建控件（TextBox测试）的线程以外的线程上执行的。如果test.InvokeRequired为真，那么您应该调用该呼叫。

Private Sub ...
    Dim powershellWorker As New BackgroundWorker
    AddHandler powershellWorker.DoWork, AddressOf BackgroundWorker1_DoWork

    powershellWorker.RunWorkerAsync()

End Sub

Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork

    If stuff <> "lol" Then
        If test.InvokeRequired Then  
            test.Invoke(Sub() test.Text = stuff)
        Else
            test.Text = stuff
        End If
    End If
End Sub

您可以使用此扩展方法自动调用所需的模式：

<Extension()>
Public Sub InvokeIfRequired(ByVal control As Control, action As MethodInvoker)
    If control.InvokeRequired Then
        control.Invoke(action)
    Else
        action()
    End If
End Sub

然后您的代码可以简化为：

Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork

    If stuff <> "lol" Then
        test.InvokeIfRequired(Sub() test.Text = stuff)
    End If
End Sub

如何在backgroundworker中更改textbox.text？

1 个答案: