如何在BackgroundWorker中调用操作RichTextBox的委托？

我创建了一个用于日志记录的委托，RichTextBox控件可见，尝试在BackgroundWorker的DoWork事件中调用该委托但无法正常工作，运行时抛出异常：无效的跨线程操作: 从不是创建控件‘RTB_Log’的线程访问它。

对应的VB.NET代码如下：

Public Class Form1
    Public Delegate Sub WriteRtbLogDelegate(ByVal Texto As String, ByVal _Color As Color)
    
    Private Sub WriteRTBLog(ByVal Texto As String, ByVal TextColor As Color)
        If Me.InvokeRequired Then
            Dim method As WriteRtbLogDelegate = AddressOf Me.WriteRTBLog
            Me.Invoke(method, Texto, TextColor)
        Else
            If RTB_Log.Lines.Length < 1 Then
                'ultima = 0
                RTB_Log.AppendText("Inicio del LOG - " & Now.ToLongDateString & vbCrLf)
            End If
    
            Dim length As Integer = RTB_Log.Text.Length
    
            Texto = Format(Now.Day, "00").ToString & "/" & Format(Now.Month, "00").ToString & "/" & Now.Year.ToString & " - " & Format(Now.Hour, "00").ToString & ":" & Format(Now.Minute, "00").ToString & ":" & Format(Now.Second, "00").ToString &
                                  " " & Texto
            RTB_Log.AppendText(Texto + vbCrLf)
            RTB_Log.SelectionStart = length
            RTB_Log.SelectionLength = Texto.Length
            RTB_Log.SelectionColor = TextColor
            ' The following expression was wrapped in a checked-expression
            RTB_Log.[Select](RTB_Log.SelectionStart + RTB_Log.SelectionLength, 0)
            RTB_Log.SelectionColor = TextColor
            RTB_Log.SelectionLength = 0
            RTB_Log.SelectionStart = RTB_Log.TextLength
            RTB_Log.ScrollToCaret()
    
            If RTB_Log.TextLength > 1000000.0 Then
                With RTB_Log
                    .SaveFile(Application.StartupPath & "\" & Format(Now.Day, "00").ToString & "-" & Format(Now.Month, "00").ToString & "-" & Now.Year.ToString & " - " &
                              Format(Now.Hour, "00").ToString & Format(Now.Minute, "00").ToString & Format(Now.Second, "00").ToString &
                              ".log", System.Windows.Forms.RichTextBoxStreamType.RichText)
                    .Clear()
                    .Text = "Log guardado en " & Application.StartupPath & Now.ToShortDateString & ".log"
                End With
            End If
        End If
    End Sub
End Class

Private Sub BGW1_DoWork(sender As Object, e As System.ComponentModel.DoWorkEventArgs) Handles BGW1.DoWork
WriteRTBLog("Starting...", Color.Blue)
End Sub

问题根源在于：代码中判断Me.InvokeRequired（Me指Form1），但跨线程访问的目标是RTB_Log控件。当BackgroundWorker的DoWork线程调用WriteRTBLog时，Me.InvokeRequired可能返回False（比如Form句柄未完全创建时），导致直接执行了访问RTB_Log的代码，触发跨线程异常。

以下两种修改方案均可解决问题：

方案一：针对RTB_Log控件判断InvokeRequired #

将线程检查的对象从Form改为RTB_Log控件，确保针对目标控件做线程同步判断：

Private Sub WriteRTBLog(ByVal Texto As String, ByVal TextColor As Color)
    ' 改为检查RTB_Log的InvokeRequired
    If RTB_Log.InvokeRequired Then
        Dim method As WriteRtbLogDelegate = AddressOf Me.WriteRTBLog
        ' 使用RTB_Log的Invoke方法
        RTB_Log.Invoke(method, Texto, TextColor)
    Else
        ' 原有日志写入逻辑保持不变
        If RTB_Log.Lines.Length < 1 Then
            RTB_Log.AppendText("Inicio del LOG - " & Now.ToLongDateString & vbCrLf)
        End If

        Dim length As Integer = RTB_Log.Text.Length

        Texto = Format(Now.Day, "00").ToString & "/" & Format(Now.Month, "00").ToString & "/" & Now.Year.ToString & " - " & Format(Now.Hour, "00").ToString & ":" & Format(Now.Minute, "00").ToString & ":" & Format(Now.Second, "00").ToString &
                      " " & Texto
        RTB_Log.AppendText(Texto + vbCrLf)
        RTB_Log.SelectionStart = length
        RTB_Log.SelectionLength = Texto.Length
        RTB_Log.SelectionColor = TextColor
        RTB_Log.[Select](RTB_Log.SelectionStart + RTB_Log.SelectionLength, 0)
        RTB_Log.SelectionColor = TextColor
        RTB_Log.SelectionLength = 0
        RTB_Log.SelectionStart = RTB_Log.TextLength
        RTB_Log.ScrollToCaret()

        If RTB_Log.TextLength > 1000000 Then
            With RTB_Log
                .SaveFile(Application.StartupPath & "\" & Format(Now.Day, "00").ToString & "-" & Format(Now.Month, "00").ToString & "-" & Now.Year.ToString & " - " &
                          Format(Now.Hour, "00").ToString & Format(Now.Minute, "00").ToString & Format(Now.Second, "00").ToString &
                          ".log", System.Windows.Forms.RichTextBoxStreamType.RichText)
                .Clear()
                .Text = "Log guardado en " & Application.StartupPath & Now.ToShortDateString & ".log"
            End With
        End If
    End If
End Sub

方案二：使用BackgroundWorker的ProgressChanged事件（更符合BGW设计） #

BackgroundWorker内置了ProgressChanged事件，该事件自动在UI线程执行，无需手动处理Invoke：

1. 启用BGW的WorkerReportsProgress属性（可在Form加载或BGW初始化时设置）：

BGW1.WorkerReportsProgress = True

2. 订阅ProgressChanged事件，在事件处理方法中写入日志：

Private Sub BGW1_ProgressChanged(sender As Object, e As ProgressChangedEventArgs) Handles BGW1.ProgressChanged
    ' 通过UserState传递日志文本和颜色，这里用Tuple封装数据
    Dim logTuple = DirectCast(e.UserState, Tuple(Of String, Color))
    WriteRTBLog(logTuple.Item1, logTuple.Item2)
End Sub

3. 在DoWork事件中调用ReportProgress触发UI更新：

Private Sub BGW1_DoWork(sender As Object, e As DoWorkEventArgs) Handles BGW1.DoWork
    ' 进度值可随意填写（如0），通过UserState传递日志数据
    BGW1.ReportProgress(0, Tuple.Create("Starting...", Color.Blue))
End Sub

这种方式贴合BackgroundWorker的设计模式，避免手动处理线程同步的潜在问题。

内容的提问来源于stack exchange，提问作者E_Blue