public void EnterSwimmersTime(Registrant registrant, string time)
        {
            TimeSpan myTime = TimeSpan.Parse("00:" + time);
            int      match  = 0;

            foreach (KeyValuePair <Registrant, Swim> entry in ListOfRegistrantSwim)
            {
                if (entry.Key == registrant)
                {
                    ListOfRegistrantSwim[registrant].TimeSwam = myTime;
                    match++;
                    Swimmer aSwimmer = registrant as Swimmer;
                    if (aSwimmer != null)
                    {
                        aSwimmer.AddAsBestTime(SwimMeet.PType, Stroke, Distance, myTime);
                    }
                }
            }
            if (match == 0)
            {
                throw new Exception(registrant.Name + " has not entered " + this.Name);
            }
        }