Shopping list

// Shopping list program

using System;
using System.Collections.Generic;
using System.IO;

class Submission
{
    // -------------------------
    // Subprograms
    // -------------------------
    static void add_item()
    {
        Console.WriteLine("Enter the item to add to the list:");
        string new_item = Console.ReadLine();
        StreamWriter file_writer = new StreamWriter("shopping.txt", true);
        file_writer.WriteLine(new_item);
        file_writer.Close();
    }

    static void output_items()
    {
        try
        {
            StreamReader file_reader = new StreamReader("shopping.txt");
            Console.WriteLine("-----------------------------");
            string file_content = file_reader.ReadToEnd();
            file_reader.Close();
            string[] items = file_content.Split(new[] { '\r', '\n' });
            foreach (string item in items)
            {
                Console.WriteLine(item.Trim());
            }
            Console.WriteLine("-----------------------------");
        }
        catch (FileNotFoundException)
        {
            StreamWriter file_writer = new StreamWriter("shopping.txt", true);
            file_writer.Close();
        }
    }

    static void sort_items()
    {
        try
        {
            StreamReader file_reader = new StreamReader("shopping.txt");
            string file_content = file_reader.ReadToEnd();
            file_reader.Close();
            string[] items = file_content.Split(new[] { '\r', '\n' });
            Array.Sort(items);
            using (StreamWriter file = new StreamWriter("shopping.txt"))
            {
                foreach (string item in items)
                {
                    file.WriteLine(item);
                }
            }
        }
        catch (FileNotFoundException)
        {
            StreamWriter file_writer = new StreamWriter("shopping.txt", true);
            file_writer.Close();
        }
    }

    static void menu()
    {
        string choice = "";
        while (choice != "4")
        {
            Console.WriteLine("1. Add item");
            Console.WriteLine("2. Output shopping list");
            Console.WriteLine("3. Sort list");
            Console.WriteLine("4. Quit");
            while (choice != "1" && choice != "2" && choice != "3" && choice != "4")
            {
                Console.WriteLine("Enter choice:");
                choice = Console.ReadLine();
            }
            // Perform function
            switch (choice)
            {
                case "1":
                    add_item();
                    choice = "";
                    break;
                case "2":
                    output_items();
                    choice = "";
                    break;
                case "3":
                    sort_items();
                    choice = "";
                    break;
            }
        }
    }

    // -------------------------
    // Main program
    // -------------------------
    public static void Main(string[] args)
    {
        menu();
    }

}