How to save / restore propertyvalue(inline.textdecorationsproperty) for a WPF richtext textrange?

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VB

WPF

How can I save / restore PropertyValue(Inline.TextDecorationsProperty) for a WPF Richtext Textrange?

My code saves / restores TextElement Properties (Bold, Italic or Font Color / Weight) but does not saves / restore values for Underline, strike through ...

Inline.TextDecorationsProperty should work for Underline - but does not work at all.

What else could I try?

What I have tried:

Public Class PropertyValues

        Public Property propVal1 As Object
        Public Property propVal2 As Object
        Public Property propVal3 As Object
        Public Property propVal4 As Object
        Public Property propVal5 As Object
        Public Property propVal6 As Object
        Public Property propVal7 As Object
        Public Property propInline As Object


Public Function SavePropertyValues(ByVal ActiveTBox As RichTextBox, ByVal selection As TextRange) As TextRange

            propInline = selection.GetPropertyValue(Inline.TextDecorationsProperty)
            propVal1 = selection.GetPropertyValue(TextElement.FontWeightProperty)
            propVal2 = selection.GetPropertyValue(TextElement.FontStyleProperty)
            propVal3 = selection.GetPropertyValue(TextElement.FontFamilyProperty)
            propVal4 = selection.GetPropertyValue(TextElement.FontSizeProperty)
            propVal5 = selection.GetPropertyValue(TextElement.FontStretchProperty)
            propVal6 = selection.GetPropertyValue(TextElement.ForegroundProperty)
            propVal7 = selection.GetPropertyValue(TextElement.BackgroundProperty)

            If propInline.Equals(TextDecorations.Underline) Then MessageBox.Show("prop 38 underline")
            If propInline.Equals(TextDecorations.Strikethrough) = True Then MessageBox.Show("strike through !")

            Return selection

End Function


Public Function RestorePropertyValues(ByVal ActiveTBox As RichTextBox, ByVal selection As TextRange) As TextRange

            If propInline.Equals(TextDecorations.Underline) = True Then
                MessageBox.Show("prop 52 underline !")
            End If

            selection.ApplyPropertyValue(Inline.TextDecorationsProperty, propInline)
            selection.ApplyPropertyValue(TextElement.FontWeightProperty, propVal1)
            selection.ApplyPropertyValue(TextElement.FontStyleProperty, propVal2)
            selection.ApplyPropertyValue(TextElement.FontFamilyProperty, propVal3)
            selection.ApplyPropertyValue(TextElement.FontSizeProperty, propVal4)
            selection.ApplyPropertyValue(TextElement.FontStretchProperty, propVal5)
            selection.ApplyPropertyValue(TextElement.ForegroundProperty, propVal6)
            selection.ApplyPropertyValue(TextElement.BackgroundProperty, propVal7)

            Return selection

End Function

End Class