public YesNoQuestion OnYes(NextQuestion onYes)
 {
     _onYes = onYes;
     return this;
 }
 public YesNoQuestion OnNo(NextQuestion onNo)
 {
     _onNo = onNo;
     return this;
 }
 public DateTimeQuestion OnNext(NextQuestion onNext)
 {
     _onNext = onNext;
     return this;
 }
 public YesNoQuestion()
 {
     _onNo = Done;
     _onYes = Done;
 }
 public DateTimeQuestion()
 {
     _onNext = Done;
 }