Kör és henger egy tömbben

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication5
{
    class Program
    {
        static void Main(string[] args)
        {
            bool ell;
            int a;
            Random RandNum = new Random();

            do
            {
                Console.WriteLine("Kérem az elemszámot:");
                ell = int.TryParse(Console.ReadLine(), out a);
            } while (!ell && a < 2);

            Kör[] RoundArray = new Kör[a];

            for (int i = 0; i < RoundArray.Length; i++)
            {
                if (RandNum.Next() % 2 == 0)
                {
                    RoundArray[i] = new Kör((RandNum.Next() % 9)+1);
                }
                else {
                    RoundArray[i] = new Henger((RandNum.Next() % 9) + 1, (RandNum.Next() % 9) + 1);
                }
                Console.WriteLine("A " + (i + 1) + ". elem tipusa: " + RoundArray[i].GetType());
                RoundArray[i].számol();
                RoundArray[i].Debug();
            }

            int maxround =-1, maxhenger = -1;
            for (int i = 0; i < RoundArray.Length; i++)
            {


                if (RoundArray[i] is Henger)
                {
                    if (maxhenger == -1)
                    {
                        maxhenger = i;
                    }
                    else
                    {
                        if ((RoundArray[i] as Henger).Terfogat > (RoundArray[maxhenger] as Henger).Terfogat)
                        {
                            maxhenger = i;
                        }
                    }
                }
                else
                {
                    if (maxround == -1)
                    {
                        maxround = i;
                    }
                    else
                    {
                        if (RoundArray[i].Area > RoundArray[maxround].Area)
                        {
                            maxround = i;
                        }
                    }

                }
            }

            Console.WriteLine("\nA legnagyobb henger: " + (maxhenger + 1) + ", térfogata: " + (RoundArray[maxhenger] as Henger).Terfogat);
            Console.WriteLine("A legnagyobb kör: " + (maxround + 1) + ", területe: " + RoundArray[maxround].Area);
        }
    }

    class Kör {
        protected int radius;
        protected double area;
        protected double kerulet;

        public int Radius
        {
            get {return radius;}
            set {radius = value;}
        }

        public double Area
        {
            get { return area; }
            set { area = value; }
        }

        public double Kerulet
        {
            get { return kerulet; }
            set { kerulet = value; }
        }

        public Kör(int setrad)
        {
            Radius = setrad;
        }

        public virtual void számol () {
            Area = Radius*Radius*3.14;
            Kerulet = 2 * 3.14 * Radius;
        }

        public virtual void Debug()
        {
            Console.WriteLine("r = " + Radius + ", K = " + Kerulet + ", T = "+ Area);
        }
    }

    class Henger : Kör {
        protected int magas;
        protected double felszin;
        protected double terfogat;

        public int Magas
        {
            get { return magas; }
            set { magas = value; }
        }

        public double Felszin
        {
            get { return felszin; }
            set { felszin = value; }
        }

        public double Terfogat
        {
            get { return terfogat; }
            set { terfogat = value; }
        }

        public override void számol()
        {
            base.számol();
            Felszin = 2 * Area + (Kerulet * Magas);
            Terfogat = Area * Magas;
        }

        public Henger(int setrad, int setmagas) : base (setrad)
        {
            Magas = setmagas;
        }

        public override void Debug()
        {
            base.Debug();
            Console.WriteLine("m = " + Magas + ", A = " + Felszin + ", V = " + Terfogat);
        }
    }
}