Internal compiler error with xaml-only

[LeftofZen]

If you attempt to create a rich text box in xaml like this:

<rtb:RichTextBox>
    <rtb:FlowDocument>
        <rtb:Paragraph>
        </rtb:Paragraph>
    </rtb:FlowDocument>
</rtb:RichTextBox>

it leads to:

Internal compiler error: Index was out of range. Must be non-negative and less than the size of the collection. (Parameter 'index') (ResolveContentPropertyTransformer). How are you supposed to use this control and bind to items in xaml?

[cuikp]

As it's setup now, you can't bind a FlowDocument via xaml in that way. The Blocks (Paragraphs) collection of the FlowDocument (FlowDoc) is manipulated in codebehind as the bound ItemsSource of an ItemsControl.

I think it can be modified to have a FlowDocument in the viewmodel that binds to the RichTextBox directly as such, but it will take some thought about how best to do it.