WPF embed C# code into xaml

<Window x:Class="WpfApp412.MainWindow"
        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:local="clr-namespace:WpfApp412"
        mc:Ignorable="d"
        WindowState="Maximized"
        WindowStyle="None"
        Title="MainWindow" Height="450" Width="800">
    <Window.Resources>
        <Style TargetType="{x:Type TextBlock}">
            <Setter Property="FontSize" Value="100"/>
        </Style>
    </Window.Resources>
    <StackPanel> 

        <Button Click="ButtonOnClick" Height="100" FontSize="30">New Content</Button>
        <TextBlock x:Name="tbk">
            <x:Code>
                <![CDATA[
                void ButtonOnClick(object sender, RoutedEventArgs args)
                {
                   Button btn=sender as Button;
                   string str=Guid.NewGuid().ToString("N");
                   //btn.Content=str;
                   tbk2.Text=str;
                }
                ]]>
            </x:Code>
        </TextBlock>
        <TextBlock x:Name="tbk2" Foreground="Red" FontSize="100" TextWrapping="Wrap"/>
    </StackPanel>
</Window>

<x:Code>
    <![CDATA[
    void ButtonOnClick(object sender, RoutedEventArgs args)
    {
       Button btn=sender as Button;
       string str=Guid.NewGuid().ToString("N");
       //btn.Content=str;
       tbk2.Text=str;
    }
    ]]>
</x:Code>