title: Throwing exception with message from regex match
body: <p>I'm trying to find unused merge fields in an email and throw the field that wasn't supported by the parser. The format is [MERGEFIELD]. All capital letters within brackets. </p>
  
  <p>I Then want to throw the value of the first unsupported merge field in the text.</p>
  
  <pre><code>            if (Regex.IsMatch(email.Body, @"\[[A-Z]+\]"))
          {
              var regexobj = new Regex(@"\[[A-Z]+\]");
              var regexBody = regexobj.Match(email.Body).Groups[1].Value;
              throw new NotImplementedException("Unsupported Merge Field:"+ regexBody );
          }
  </code></pre>
  
  <p>Right now I'm getting the exception, but there only message is "Unsupported Merge Field:"</p>