Add-Type usage?

I have some code:

      $authTicketRepresentationSource = @"

    public class AuthorizationTicketRepresentation`
    {`
        public string TicketId { get; set; }
        public string Username { get; set; }
        public string ClientIpAddress { get; set; }
        public string Owner { get; set; }
        public DateTime CreationTime { get; set; }
        public DateTime ExpirationTime { get; set; }
        public string ResourceId { get; set; }
        public int MinutesToLive { get; set; }
    }
"@

      $authTicketRepresentation = Add-Type -TypeDefinition $authTicketRepresentationSource -Name "AuthorizationTicketRepresentation" -PassThru

But when I call Add-Type as above I get an exception 'Parameter set cannot be resolved using the specified named parameters.'

What am I doing wrong? How can I get this type available to the PowerShell script?

Thank you.

---

Kevin Burton