List of numbers sum

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

namespace CollectionsTask3DynamicArray
{
    internal class Program
    {
        static void Main(string[] args)
        {
            const string CommandExit = "exit";
            const string CommandSum = "sum";
            const string CommandNew = "new";

            List <int> numbers = new List <int> ();
            bool isRunning = true;
            string userInput;

            Console.WriteLine($"Здравствуйте! Введите число для добавления в массив или команды {CommandExit}, {CommandSum} или {CommandNew}!");

            while (isRunning)
            {
                PrintList(numbers);
                userInput = Console.ReadLine();

                switch (userInput)
                {
                    case CommandExit:
                        isRunning = false;
                        break;
                    case CommandNew:
                        numbers.Clear ();
                        break;
                    case CommandSum:
                        Console.WriteLine($"Сумма элементов списка: {CalcSum(numbers)}");
                        break;
                    default:
                        ConvertAndAddIfElementIsNumber(userInput, numbers);
                        break;
                }
            }
        }

        private static void PrintList(List<int> list)
        {
            foreach (int item in list)
            {
                Console.Write($"{item} ");
            }

            Console.WriteLine();
        }

        private static int CalcSum(List<int> list)
        {
            int sum = 0;

            foreach (int item in list)
            {
                sum += item;
            }

            return sum;
        }

        private static void ConvertAndAddIfElementIsNumber(string element, List <int> list)
        {
            int inputNumber;

            if (int.TryParse(element, out inputNumber))
            {
                list.Add(inputNumber);
            }
            else
            {
                Console.WriteLine("Введено не число.");
            }
        }
    }
}