title: TimeSpan.ToString() return string like (d:hh:mm:ss)
body: <pre><code>TimeSpan Ts = new TimeSpan(5, 4, 3, 2);
  return Ts.ToString("?");
  </code></pre>
  
  <p>What expression should I replace with a question mark to get this format:
  <strong><em>5d:4h:3m:2s</em></strong> ?</p>