title: How do I convert an ISO8601 TimeSpan to a C# TimeSpan?
body: <p>I am getting a <code>System.FormatException</code> when I try to do the following (as an example):</p>
  
  <pre><code>TimeSpan ts = XmlConvert.ToTimeSpan("P72H");
  </code></pre>
  
  <p>I've investigated the <a href="http://en.wikipedia.org/wiki/ISO_8601#Dates" rel="noreferrer">ISO8601 Standard</a> and it seems to be correct, but I cannot get it to parse hours without throwing an exception, no matter what I do.</p>
  
  <p>Thanks!</p>
  
  <p>EDIT: </p>
  
  <p>Exception detail:</p>
  
  <pre><code>System.FormatException was unhandled by user code
  HResult=-2146233033
  Message=The string 'P72H' is not a valid TimeSpan value.
  Source=System.Xml
  </code></pre>