Динамический_массив

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

namespace Динамический_массив
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] numbers = new int[0];
            string userInput;
            int userNumbers;
            bool isWork = true;
            while (isWork)
            {
                Console.Write("Ввод: ");
                userInput = Console.ReadLine();
                switch (userInput)
                {
                    case "exit":
                        Console.WriteLine("Выход...");
                        isWork = false;
                        break;
                    case "sum":
                        Console.WriteLine("Подсчет...");
                        int sum = 0;
                        for (int i = 0; i < numbers.Length; i++)
                        {
                            sum += numbers[i];
                        }
                        Console.WriteLine("Сумма: " + sum);
                        break;
                    default:
                        userNumbers = Convert.ToInt32(userInput);
                        int[] tempNumbers = new int[numbers.Length + 1];
                        for (int i = 0; i < numbers.Length; i++)
                        {
                            tempNumbers[i] = numbers[i];
                        }
                        tempNumbers[tempNumbers.Length - 1] = userNumbers;
                        numbers = tempNumbers;
                        break;
                }
            }
        }
    }
}