寻找特定形状的RunProperty（pptx）

Question

我只想从标题形状中获取字体大小，但我的代码会检查所有形状的RunProperties：

Public Function GetSlideTitle(ByVal slidePart As SlidePart) As String()

    If (Not (slidePart.Slide) Is Nothing) Then

        ' Find all the title shapes.
        Dim shapes = From shape In slidePart.Slide.Descendants(Of Shape)() _
         Where (IsTitleShape(shape)) _
         Select shape

        Dim paragraphText As StringBuilder = New StringBuilder
        Dim minFont As Double = 200000
        Dim maxfont As Double = 0

''''getting the text from the title shapes - this works fine

        For Each shape As Object In shapes
            For Each paragraph As Drawing.Paragraph In shape.TextBody.Descendants(Of D.Paragraph)()
                For Each text As Object In paragraph.Descendants(Of D.Text)()
                    paragraphText.Append(text.Text)
                Next
            Next
        Next

'''' This is the part in question:

        Dim runProList As Drawing.RunProperties() = slidePart.Slide.Descendants(Of Drawing.RunProperties)().ToArray()

        For Each r As Drawing.RunProperties In runProList
            If Not IsNothing(r) AndAlso Not IsNothing(r.FontSize) Then
                If r.FontSize.Value > 0 AndAlso minFont > r.FontSize.Value Then minFont = r.FontSize.Value
                If maxfont < r.FontSize.Value Then maxfont = r.FontSize.Value
            End If
        Next


        Return New String() {paragraphText.ToString, minFont.ToString, maxfont.ToString}
    End If
    Return New String() {String.Empty}
End Function

我如何知道哪个RunProperty属于给定的形状？