title: How to assign a Run to a text property, programmatically?
body: <p>I know in XAML we can do...</p>
  
  <pre><code>&lt;TextBlock FontSize="18"&gt;
     This is my text &lt;LineBreak/&gt;
     &lt;Run FontSize="24" FontWeight="Bold"&gt;My big bold text&lt;/Run&gt;
  &lt;/TextBlock&gt;
  </code></pre>
  
  <p>Question is, how can I assign a Run into a text (string) property, programmatically?</p>