title: How to calculate an age based on a birthday
body: <blockquote>
  <p><strong>Possible Duplicate:</strong> <br />
  <a href="https://stackoverflow.com/questions/9/how-do-i-calculate-someones-age-in-c">How do I calculate someone's age based on a DateTime type birthday?</a></p>
  </blockquote>
  
  <p>I want to write an ASP.NET helper method which returns the age of a person given his or her birthday.</p>
  <p>I've tried code like this:</p>
  <pre><code>public static string Age(this HtmlHelper helper, DateTime birthday)
  {
      return (DateTime.Now - birthday); //??
  }
  </code></pre>
  <p>But it's not working. What is the correct way to calculate the person's age based on their birthday?</p>