Dynamic array advanced(2)

using System;
using System.Collections.Generic;

namespace ConsoleApp3
{
    internal class Program
    {
        static void Main(string[] args)
        {
            const string CommandSum = "sum";
            const string CommandExit = "exit";
            const string CommandPrint = "print";

            bool isRuning = true;
            List<int> numbers = new List<int>();

            while (isRuning)
            {
                Console.Write("Введите команду или число: ");
                string userInput = Console.ReadLine();

                switch (userInput)
                {
                    case CommandSum:
                        SumNumbers(numbers);
                        break;

                    case CommandExit:
                        isRuning = false;
                        break;

                    case CommandPrint:
                        PrintNumbers(numbers);
                        break;

                    default:
                        AddNumber(numbers, userInput);
                        break;
                }
            }
        }

        static void SumNumbers(List<int> numbers)
        {
            int sum = 0;

            foreach (int number in numbers)
                sum += number;

            Console.WriteLine("Сумма чисел равна " + sum);
        }

        static void AddNumber(List<int> numbers, string userInput)
        {
            if (int.TryParse(userInput, out int number))
                numbers.Add(number);
            else
                Console.WriteLine("Введите целое число!");
        }

        static void PrintNumbers(List<int> numbers)
        {
            foreach (int number in numbers)
                Console.Write(number + " ");

            Console.WriteLine();
        }
    }
}