Студент 221's questions

对于本程序，实现按照选项（见表）将查询结果输出到文件中。

选项：显示商店中可用产品的所有信息（由用户输入）[已取消]总之，我把表中的选项搞乱了，我只需要将它输出到文件中即可。

代码：

Program
static void Main(string[] args)
{
    Storage stock = new Storage(3);
    stock[0] = new Tovar("01", "Товар1", "Магазин5", 4300);
    stock[1] = new Tovar("02", "Товар2", "Магазин7", 5340);
    stock[2] = new Tovar("03", "Товар3", "Магазин3", 3040);

    bool auditor = true;
    while (auditor)
    {

        Console.WriteLine("\nВведите тип операции");
        Console.WriteLine("1) Найти товар по ID");
        Console.WriteLine("2) Найти товар по названию");
        Console.WriteLine("3) Отсортировать массив товаров по цене");
        Console.WriteLine("4) Отсортировать массив товаров по названию");
        Console.WriteLine("5) Отсортировать массив товаров по магазину");
        Console.WriteLine("6) Закончить");

        string number = Console.ReadLine();
        Console.WriteLine();

        switch (number)
        {
            case "1":
                string search_ID = Console.ReadLine();
                Tovar  item0 = stock.FindProductID(search_ID);
                if (item0 != null)
                    Console.WriteLine(item0.ToString());
                break;
            case "2":
                string search_name = Console.ReadLine();
                Tovar item1 = stock.FindProductName(search_name);
                if (item1 != null)
                    Console.WriteLine(item1.ToString());
                else Console.WriteLine("Нет такого");
                break;
            case "3":
                Tovar[] tests = stock.SortByCost();
                for (int i = 0; i < tests.Length; i++)
                {
                    Console.WriteLine(tests[i].ToString());
                }
                break;
            case "4":
                Tovar[] tests1 = stock.SortByName();
                for (int i = 0; i < tests1.Length; i++)
                {
                    Console.WriteLine(tests1[i].ToString());
                }
                break;
            case "5":
                Tovar[] tests2 = stock.SortByShop();
                for (int i = 0; i < tests2.Length; i++)
                {
                    Console.WriteLine(tests2[i].ToString());
                }
                break;
            case "6":
                auditor = false;        
                break;
        }
    }
    Console.WriteLine();
    
    Console.WriteLine("Сумма товаров:");
    Console.WriteLine(stock[0] + stock[1]);
    Console.ReadKey();
}

internal class Tovar
{
    public string ID { get; private set; } //что бы явно не обявлять резервную переменную
    public string Name { get; private set; }
    public string Shop { get; private set; }
    public double Cost { get; private set; }
    public Tovar(string id, string name, string shop, double cost)
    {
        ID = id;
        Name = name;
        Shop = shop;
        Cost = cost;
    }
    public override string ToString()
    {
        return $"ID: {ID}, название: {Name}, магазин: {Shop}, цена: {Cost}";
    }
    public static double operator +(Tovar obj1, Tovar obj2)
    {
        return obj1.Cost + obj2.Cost;
    }
}

internal class Storage
{
    Tovar[] products;
    public int Length { get; private set; }
    public Storage(int length)
    {
        Length = length;
        products = new Tovar[Length];
    }

    public Tovar this[int index]
    {
        get
        {
            if (IsValid(index))
                return products[index];
            throw new IndexOutOfRangeException();
        }
        set
        {
            if (IsValid(index))
                products[index] = value;
            else
                throw new IndexOutOfRangeException();
        }
    }

    public Tovar FindProductID(string id)
    {
        foreach (Tovar item0 in products)
        {
            if (item0.ID == id)
                return item0;
        }
        return null;
    }

    public Tovar FindProductName(string name)
    {
        foreach (Tovar item1 in products)
        {
            if (item1.Name == name)
                return item1;
        }
        return null;
    }
    public Tovar[] SortByName()
    {
        return products.OrderBy(n => n.Name).ToArray();
    }
    public Tovar[] SortByShop()
    {
        return products.OrderBy(n => n.Shop).ToArray();
    }
    public Tovar[] SortByCost()
    {
        return products.OrderBy(n => n.Cost).ToArray();
    }
    private bool IsValid(int index)
    {
        return (index >= 0) && (index < Length);
    }
}

问题：代码中需要添加什么才能将所有信息输出到文件中？

简而言之，我的作业要求我演示 Directory 和 DirectoryInfo 类的操作。当我输入一种方法的测试示例时，我收到一条错误消息，表明该方法名称在当前上下文中不存在。我最终该如何解决这个问题？我附上下面的代码。

internal class Directory
{
    static void Main(string[] args)
    {
        string dirName = "E:\\";
        if (Directory.Exists(dirName)) //<-вот здесь на Exists
        {
            Console.WriteLine("Подкаталоги:");
            string[] dirs = Directory.GetDirectories(dirName); //<-и здесь на GetDirectories
            foreach (string s in dirs)
            {
                Console.WriteLine(s);
            }
            Console.WriteLine();
            Console.WriteLine("Файлы:");
            string[] files = Directory.GetFiles(dirName); //<-и тут на GetFiles
            foreach (string s in files)
            {
                Console.WriteLine(s);
            }
        }

    }
}