What is the use of x:code ?

x:Code is a directive element defined in XAML. An x:Code directive element can contain inline programming code. The code that is defined inline can interact with the XAML on the same page. The following example illustrates inline C# code. Notice that the code is inside the x:Code element and that the code must be surrounded by <CDATA[…]]> to escape the contents for XML, so that an XAML processor (interpreting either the XAML schema or the WPF schema) will not try to interpret the contents literally as XML.

[XAML]

<Page
  xmlns='http://schemas.microsoft.com/winfx/2006/xaml/presentation'
  xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
  x:Class='MyNamespace.MyCanvasCodeInline'
>
  <Button Name='button1' Click='Clicked'>Click Me!</Button>
  <x:Code><![CDATA[
    void Clicked(object sender, RoutedEventArgs e)
    {
        button1.Content = 'Hello World';
    }
  ]]></x:Code>
</Page>