Как перейти на нужную строку в RichTextBox?

' Create a new FlowDocument, and add 3 paragraphs.
Dim flowDoc As New FlowDocument()
flowDoc.Blocks.Add(New Paragraph(New Run("Paragraph 1")))
flowDoc.Blocks.Add(New Paragraph(New Run("Paragraph 2")))
flowDoc.Blocks.Add(New Paragraph(New Run("Paragraph 3")))
' Set the FlowDocument to be the content for a new RichTextBox.
Dim rtb As New RichTextBox(flowDoc)
 
' Get the current caret position.
Dim caretPos As TextPointer = rtb.CaretPosition
 
' Set the TextPointer to the end of the current document.
caretPos = caretPos.DocumentEnd
 
' Specify the new caret position at the end of the current document.
rtb.CaretPosition = caretPos

' This method returns the position just inside of the first text Run (if any) in a 
' specified text container.
Private Function FindFirstRunInTextContainer(ByVal container As DependencyObject) As TextPointer
    Dim position As TextPointer = Nothing
 
    If container IsNot Nothing Then
        If TypeOf container Is FlowDocument Then
            position = (CType(container, FlowDocument)).ContentStart
        ElseIf TypeOf container Is TextBlock Then
            position = (CType(container, TextBlock)).ContentStart
        Else
            Return position
        End If
    End If
    ' Traverse content in forward direction until the position is immediately after the opening 
    ' tag of a Run element, or the end of content is encountered.
    Do While position IsNot Nothing
        ' Is the current position just after an opening element tag?
        If position.GetPointerContext(LogicalDirection.Backward) = TextPointerContext.ElementStart Then
            ' If so, is the tag a Run?
            If TypeOf position.Parent Is Run Then
                Exit Do
            End If
        End If
 
        ' Not what we're looking for on to the next position.
        position = position.GetNextContextPosition(LogicalDirection.Forward)
    Loop
 
    ' This will be either null if no Run is found, or a position just inside of the first Run element in the
    ' specifed text container.  Because position is formed from ContentStart, it will have a logical direction
    ' of Backward.
    Return position
End Function

Me.RichTextBox1.Select([позиция], 0)

    Public Sub SetCaretToRow(ByVal RowIndex As Integer, RTB As RichTextBox)
 
        Dim r As Integer = 0
        Dim s As Integer = 0
 
        For Each c As Char In RTB.Text
            If r = RowIndex Then
                RTB.Select(s, 0)
                RTB.Focus() ' нужно в случае если производится управление с другого элемента управления
                Return
            End If
            If c = vbLf Then
                r += 1
            End If
            s += 1
        Next
 
        'Throw New OverflowException("Индекс выходит за пределы коллекции") ' для контроля
 
    End Sub

    ' RowIndex - номер строки с ноля с учетом переносов
    Public Sub SetCaretToRow(ByVal RowIndex As Integer, ByVal RTB As RichTextBox)
        Dim PosInd As Integer
        PosInd = RTB.GetFirstCharIndexFromLine(RowIndex) 
        If PosInd >= 0 Then
            RTB.Select(PosInd, 0)
            RTB.Focus()
        Else
            ' нет такой строки
        End If
    End Sub