title: Check if a number in a string contains a valid year in c#
body: <p>I have a the following string and need to ensure that the number in the string is a valid year. So in this case 2014.</p>
  
  <pre><code>var notesField = "Payment for the month ending 30 Nov 2014";
  char[] whitespace = new char[] { ' ', '\t' };
  string[] text = notesField.Split(
                            whitespace,
                            StringSplitOptions.RemoveEmptyEntries
                            );
  </code></pre>