Ошибка "Элемент не существует в текущем контексте" - C# (182561)

namespace третье_целиком_
{
    class Purchase : IComparable<Purchase>
    {
        private string name;
        private double cena;
        private int kol;
        private Days fieldName;
        enum Days { Sun, Mon, Tue, Wed, Thu, Fri, Sat };
 
        public int CompareTo(Purchase obj)
        {
            if (this.GetCost() > obj.GetCost())
                return 1;
            if (this.GetCost() < obj.GetCost())
                return -1;
 
            else
                return 0;
        }
        public Purchase(string newName, double newCena, int newKol, Days days)
        {
            Cena = newCena;
            Name = newName;
            Kol = newKol;
            fieldName =(Days)days;
        }
 
        public Purchase()
        {
        }
 
        public string Name
        {
            get
            {
                return name;
            }
            set
            {
                name = value;
            }
        }
 
        public double Cena
        {
            get
            {
                return cena;
            }
            set
            {
                cena = value;
            }
        }
 
        public int Kol
        {
            get
            {
                return kol;
            }
            set
            {
                kol = value;
            }
        }
 
        public string FieldName
        { get { return fieldName.ToString(); } }

        public double GetCost()
        {
            return (Cena * Kol);
        }
 
        public override string ToString()
        {
            return string.Format("{0};{1};{2};{3};{4}", Name, Cena, Kol, fieldName, GetCost());
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
 
namespace третье_целиком_
{
    class Program
    {
        static void Main(string[] args)
        {
            double prodsum = 0;

            Purchase[] prod = new Purchase[5];
            prod[0] = new Purchase("limon", 4, 6, Sun);
            prod[1] = new Purchase("tea", 2, 2, Sun);
            prod[2] = new Purchase("coffe", 2, 1, Sun);
            prod[3] = new Purchase("ice-cream", 1, 20, Sun);
            prod[4] = new Purchase("sugar", 1.5, 15, Sun);
 
            foreach (var element in prod)
            {
                System.Console.WriteLine(element);
            }

            for (int i = 0; i < prod.Length; i++)
            {
                prodsum += prod[i].GetCost();
            };
            Purchase maxP = prod[0];
 
            for (int i = 0; i < prod.Length; i++)
            {
                if (maxP.GetCost() < prod[i].GetCost())
                {
                    maxP = prod[i];
                }
            };
            Console.WriteLine();
            Console.WriteLine("среднее арефмитическое: {0}", prodsum / prod.Length);
            Console.WriteLine();
            Console.WriteLine("день макс. покупки : {0}", maxP.FieldName);
            Console.WriteLine();
            Array.Sort(prod);
            foreach (var element in prod)
            {
                System.Console.WriteLine(element);
            }
            Console.ReadKey();
        }
    }
}