MainView.xaml

<UserControl
    x:Class="CSharpMath.Avalonia.Example.MainView"
    xmlns="https://github.com/avaloniaui"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:pages="clr-namespace:CSharpMath.Avalonia.Example.Pages"
    Background="{DynamicResource ThemeBackgroundBrush}"
    FontSize="{DynamicResource FontSizeNormal}"
    Foreground="{DynamicResource ThemeForegroundBrush}">

    <DockPanel>

        <StackPanel
            HorizontalAlignment="Right"
            DockPanel.Dock="Bottom"
            Orientation="Horizontal">
            <RadioButton
                x:Name="lightThemeRbn"
                Margin="2,8"
                Padding="8,0"
                VerticalContentAlignment="Center"
                Content="Light"
                IsChecked="true" />
            <RadioButton
                Margin="2,8"
                Padding="8,0"
                VerticalContentAlignment="Center"
                Content="Dark" />
        </StackPanel>

        <TabControl x:Name="Sidebar" Padding="16">
            <TabItem Header="MathView">
                <pages:MathViewPage />
            </TabItem>
            <TabItem Header="TextView">
                <pages:TextViewPage />
            </TabItem>
            <TabItem Header="MathButton">
                <pages:MathButtonPage />
            </TabItem>
            <TabItem Header="Calculator">
                <pages:CalculatorPage />
            </TabItem>
        </TabControl>

    </DockPanel>

</UserControl>