Dispatcher.BeginInvoke VB 错误，但不是 C#

Question

嘿，我正在使用一些用 C# 编写的 UIAutomation 代码。所以我把它转换成 VB.net 这样我就可以将它集成到我自己制作的程序中。

出错的代码是这一行：

Private Sub LogMessage(message As String)
    Dispatcher.BeginInvoke(DispatcherPriority.Normal, New SetMessageCallback(AddressOf DisplayLogMessage), message)
End Sub

错误在 Dispatcher.BeginInvoke 上，指出 错误 1 对非共享成员的引用需要对象引用。 .

C# 中的代码如下所示：

private void LogMessage(string message)
{
    this.Dispatcher.BeginInvoke(DispatcherPriority.Normal, new SetMessageCallback(DisplayLogMessage), message);
}

没有错误，工作正常。

VB.net 版本中缺少什么才能使其正常工作？

可以找到原始的 C# 代码 HERE。

我将 C# 转换为 VB.net 的代码如下所示：

Imports System.Threading
Imports Automation = System.Windows.Automation
Imports System.Windows.Automation
Imports System.Windows.Threading

Public Class Form1
    Public Delegate Sub SetMessageCallback(ByVal [_Msg] As String)

    Private Sub Automate()
        LogMessage("Getting RootElement...")
        Dim rootElement As AutomationElement = AutomationElement.RootElement
        If rootElement IsNot Nothing Then
            LogMessage("OK." + Environment.NewLine)

            Dim condition As Automation.Condition = New PropertyCondition(AutomationElement.NameProperty, "UI Automation Test Window")

            LogMessage("Searching for Test Window...")
            Dim appElement As AutomationElement = rootElement.FindFirst(TreeScope.Children, condition)

            If appElement IsNot Nothing Then
                LogMessage("OK " + Environment.NewLine)
                LogMessage("Searching for TextBox A control...")
                Dim txtElementA As AutomationElement = GetTextElement(appElement, "txtA")
                If txtElementA IsNot Nothing Then
                    LogMessage("OK " + Environment.NewLine)
                    LogMessage("Setting TextBox A value...")
                    Try
                        Dim valuePatternA As ValuePattern = TryCast(txtElementA.GetCurrentPattern(ValuePattern.Pattern), ValuePattern)
                        valuePatternA.SetValue("10")
                        LogMessage("OK " + Environment.NewLine)
                    Catch
                        WriteLogError()
                    End Try
                Else
                    WriteLogError()
                End If

                LogMessage("Searching for TextBox B control...")
                Dim txtElementB As AutomationElement = GetTextElement(appElement, "txtB")
                If txtElementA IsNot Nothing Then
                    LogMessage("OK " + Environment.NewLine)
                    LogMessage("Setting TextBox B value...")
                    Try
                        Dim valuePatternB As ValuePattern = TryCast(txtElementB.GetCurrentPattern(ValuePattern.Pattern), ValuePattern)
                        valuePatternB.SetValue("5")
                        LogMessage("OK " + Environment.NewLine)
                    Catch
                        WriteLogError()
                    End Try
                Else
                    WriteLogError()
                End If
            Else
                WriteLogError()
            End If
        End If
    End Sub

    Private Function GetTextElement(parentElement As AutomationElement, value As String) As AutomationElement
        Dim condition As Automation.Condition = New PropertyCondition(AutomationElement.AutomationIdProperty, value)
        Dim txtElement As AutomationElement = parentElement.FindFirst(TreeScope.Descendants, condition)
        Return txtElement
    End Function

    Private Sub DisplayLogMessage(message As String)
        TextBox1.Text += message
    End Sub

    Private Sub LogMessage(message As String)
        Me.Dispatcher.BeginInvoke(DispatcherPriority.Normal, New SetMessageCallback(AddressOf DisplayLogMessage), message)
    End Sub

    Private Sub WriteLogError()
        LogMessage("ERROR." + Environment.NewLine)
    End Sub

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim automateThread As New Thread(New ThreadStart(AddressOf Automate))
        automateThread.Start()
    End Sub
End Class

Answer 1

Dispatcher可以是静态的。我想你需要 Me.Dispatcher.

Answer 2

找到正确的方法：

Private Sub LogMessage(message As String)
    Me.BeginInvoke(New SetMessageCallback(AddressOf DisplayLogMessage), message)
End Sub

感谢@HansPassant 的帮助。

Dispatcher.BeginInvoke VB 错误，但不是 C#

Dispatcher.BeginInvoke Error in VB but not C#

c#

vb.net

ui-automation

microsoft-ui-automation