Example test of trying to re-style a `RadioButtons` control to look like a Segmented Control.

SegmentedControlTest.xaml

<!-- See Reference Issues:
        https://github.com/microsoft/microsoft-ui-xaml/issues/2310
        https://github.com/microsoft/microsoft-ui-xaml/issues/3759
-->
<Page
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:muxc="using:Microsoft.UI.Xaml.Controls"
    xmlns:primitives="using:Microsoft.UI.Xaml.Controls.Primitives"
    mc:Ignorable="d">

    <Page.Resources>
        <Style x:Key="SegmentedToggleButtonStyle" BasedOn="{StaticResource DefaultToggleButtonStyle}" TargetType="ToggleButton">
            <Setter Property="Background" Value="Transparent"/>
            <Setter Property="CornerRadius" Value="12"/>
            <Setter Property="Padding" Value="12,0,12,0"/>
        </Style>

        <DataTemplate x:Key="SegmentedRadioButtonsItemTemplate">
            <ToggleButton Content="{Binding}"
                          Style="{StaticResource SegmentedToggleButtonStyle}"/> <!-- TODO: Bind to SelectedItem of parent? -->
        </DataTemplate>
        
        <Style x:Key="SegmentedRadioButtons" TargetType="muxc:RadioButtons">
            <Setter Property="MaxColumns" Value="100"/> <!-- Workaround for Layout not being exposed: https://github.com/microsoft/microsoft-ui-xaml/issues/2084 -->
            <Setter Property="ItemTemplate" Value="{StaticResource SegmentedRadioButtonsItemTemplate}"/>
            <Setter Property="TabNavigation" Value="Once"/>       
            <Setter Property="SelectedIndex" Value="0"/>
        </Style>                
    </Page.Resources>

    <!-- Had issues in XAML Studio for some reason copying and overriding the RadioButtons style, so used border here
         to work around https://github.com/microsoft/microsoft-ui-xaml/issues/3247 -->
    <Border BorderBrush="{ThemeResource SystemControlForegroundBaseMediumHighBrush}" BorderThickness="{ThemeResource RadioButtonBorderThemeThickness}"
            CornerRadius="16"
            Padding="2"
            HorizontalAlignment="Center" VerticalAlignment="Center">
        <muxc:RadioButtons Style="{StaticResource SegmentedRadioButtons}">
            <muxc:RadioButtons.Resources>
                <x:Double x:Key="RadioButtonsColumnSpacing">0</x:Double>
            </muxc:RadioButtons.Resources>
            <x:String>None</x:String>
            <x:String>Some</x:String>
            <x:String>All</x:String>
        </muxc:RadioButtons>
    </Border>
</Page>