CodeView.xaml

<?xml version="1.0" encoding="utf-8"?>
<Window
    x:Class="VisualWinUI3.CodeView"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:VisualWinUI3"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d"
    Title="CodeView">

<Grid>
	<Grid.RowDefinitions>
		<RowDefinition Height="Auto"/>
        <RowDefinition Height="*"/>
    </Grid.RowDefinitions>

        <StackPanel Orientation="Horizontal" Grid.Row="0" Margin="10">
            <SelectorBar x:Name="SelectorBar1" Grid.Row="0" SelectionChanged="LVC">
                <SelectorBarItem Text="IDL" Icon="Memo" x:Name="si0" />
                <SelectorBarItem Text="XAML" Icon="Edit" x:Name="si1"/>
                <SelectorBarItem  Text="H" Icon="Document" x:Name="si2"/>
                <SelectorBarItem  Text="CPP" Icon="Document" x:Name="si3"/>
            </SelectorBar>
            <Button ToolTipService.ToolTip="{x:Bind txt(80)}" Click="CopyCode" Style="{ThemeResource AccentButtonStyle}">
                <SymbolIcon Symbol="Copy"/>
                <Button.Flyout>
                    <Flyout Placement="Bottom">
                        <TextBlock Text="{x:Bind txt(4);}" />
                    </Flyout>
                </Button.Flyout>
            </Button>
        </StackPanel>

        <ScrollViewer Grid.Row="1" Margin="10" VerticalScrollBarVisibility="Auto">
            <RichTextBlock  x:Name="rtb">
            </RichTextBlock>
        </ScrollViewer>
    </Grid>
</Window>