public void HirePersonel(Personel person)
 {
     if (this.WorkPlace == null)
     {
         throw new PersonException("I'm unemployed! Please hire me!");
     }
     this.WorkPlace.HirePersonel(person);
 }
 public virtual void HirePersonel(Personel person)
 {
     this.Personel.Add(person);
     person.WorkPlace = this;
 }