title: Binding window title to child property
body: <p>I've got a window with my custom textbox-like control on it</p>
  
  <pre><code>&lt;Window.Title&gt;
      &lt;Binding ElementName="codeBox" Path="Filename" UpdateSourceTrigger="PropertyChanged" /&gt;
  &lt;/Window.Title&gt;
  ...
  &lt;custom:CodeArea Name="codeBox"&gt;
  &lt;/custom:CodeArea&gt;
  </code></pre>
  
  <p>here what I have inside my CodeArea back code (CodeArea.xaml.cs)</p>
  
  <pre><code>private string _filename = "NoName";
  public string Filename
  {
      get { return _filename; }
      set { _filename = value; }
  }
  </code></pre>
  
  <p>When application starts, it has 'NoName' title. If I open any file, Filename setter <em>is</em> called, but title doesn't change. What I'm doing wrong?</p>