How do we present TabViewItem content

[mwpowellhtx]

I am trying to arrange some <Label/> and such in the a <ui:TabViewItem/>, but does not seem to be showing the text properly. I do not know if it is a font family thing, size, color, what have you, or I need to be doing something more XAML-y, if you will, to persuade the content to be rendered properly, in a design mode, let alone runtime. Note, ultimately, will also like to integrate Markup Extensions, for things like property DisplayNameAttribute annotations, but keeping it somewhat simple until I can establish a repeatable (successful) pattern.

<ui:TabViewItem DataContext="{Binding General}" Header="{Binding TabViewItemHeader, Mode=OneWay}">
    <ui:TabViewItem.Content>
        <Grid>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="1*" />
                <ColumnDefinition Width="3*" />
            </Grid.ColumnDefinitions>
            <Label Grid.ColumnSpan="1" Content="Test" Width="auto" HorizontalAlignment="Right" />
        </Grid>
    </ui:TabViewItem.Content>
</ui:TabViewItem>

The text "Test" is not appearing in the designer. I have tried with <ui:TabViewItem.Content/> and without i.e. just <Grid/> to no avail.

Eventually, I also want to do something like this, but not before I get the basic result I am aiming toward.

<Label Grid.ColumnSpan="1" Content="{vm:DisplayName PropertyName=Uuid}" Width="auto" HorizontalAlignment="Right" />

The actual <ui:TabViewItem Header="..." /> binding is working correctly, so I am at least confident that the data contexts are correct.

Ideas, suggestions? 💡 🧠

Thanks...