title: WPF RichTextBox - Language not preserved
body: <p>I have a <code>RichTextBox</code> in my WPF application, which has a <code>Run</code> in its <code>FlowDocument</code>. The XAML code looks something like this:</p>
  
  <pre><code>&lt;RichTextBox&gt;
      &lt;FlowDocument&gt;
          &lt;Paragraph&gt;
              &lt;Bold&gt;
                  &lt;Run xml:lang="nl-be"&gt;My name is Mark.&lt;/Run&gt;
              &lt;/Bold&gt;
          &lt;/Paragraph&gt;
      &lt;/FlowDocument&gt;
  &lt;/RichTextBox&gt;
  </code></pre>
  
  <p>Trying to type anything at all into the <code>RichTextBox</code>, the language will instantly change for all of the text to my own language, <code>nb-NO</code>.</p>
  
  <p>This is not normal behavior. If you do the same with the <code>Bold</code>-property, anything you insert in the middle or at the end of the text will inherit the <code>Bold</code>-property.</p>
  
  <p>Does anyone know why this happens? Any workarounds?</p>
  
  <ul>
  <li><a href="http://www.mediafire.com/?e9sn69a0kb2n8bw" rel="nofollow noreferrer">A working example</a>.</li>
  </ul>
  
  <p>Screenshot:</p>
  
  <p><img src="https://i.imgur.com/LPwSDrW.png" alt="Screenshot">.</p>