[ActiveRecord]
    public class Usuario : ActiveRecordBase {
        private int id;
       // other properties
        private Club club;

        [PrimaryKey]
        public int Id {
            get { return id;}
            set { id = value; }
        }

      // getters & setters

        [BelongsTo("ClubId")]
        public Club Club {
            get { return club; }
            set { club = value; }
        }

      // other methods
    }