public TimeSlot Begin()
 {
     Status = TimeSlotStatus.InProgress;
     return(this);
 }
 public TimeSlot End()
 {
     Status = TimeSlotStatus.Completed;
     return(this);
 }
 public TimeSlot(DateTime startTime)
 {
     StartTime = startTime;
     _status   = TimeSlotStatus.Awaiting;
 }