public override string Manifest(object o)
{
if (o is ClusterReceptionist.Contacts) return ContactsManifest;
if (o is ClusterReceptionist.GetContacts) return GetContactsManifest;
if (o is ClusterReceptionist.Heartbeat) return HeartbeatManifest;
if (o is ClusterReceptionist.HeartbeatRsp) return HeartbeatRspManifest;
throw new ArgumentException(string.Format("Can't serialize object of type [{0}] in [{1}]", o.GetType(), GetType()));
}