#23

            const string CommandExit = "exit";
            const string CommandSum = "sum";

            string inputMessage;

            int numberIput;
            int[] arrayNumbers = new int[0];

            bool isWorking = true;

            while (isWorking)
            {
                Console.Clear();
                Console.Write("Массив: ");

                for (int i = 0; i < arrayNumbers.Length; i++)
                {
                    Console.Write(arrayNumbers[i] + " ");
                }

                Console.WriteLine($"\nСписок комманд:\n1--->{CommandSum}\n2--->{CommandExit}");
                Console.Write("Введите число или команду: ");
                inputMessage = Console.ReadLine();

                switch (inputMessage.ToLower())
                {
                    case CommandSum:
                        int arraySumNumbers = 0;

                        for (int i = 0; i < arrayNumbers.Length; i++)
                        {
                            arraySumNumbers += arrayNumbers[i];
                        }

                        Console.WriteLine($"Сумма массива: {arraySumNumbers} ");
                        arraySumNumbers = 0;

                        Console.Write("Нажмите 'enter' для продолжения");
                        Console.ReadKey();
                        break;

                    case CommandExit:
                        Console.WriteLine("До свидания!");
                        isWorking = false;
                        break;

                    default:
                        numberIput = Convert.ToInt32(inputMessage);
                        int[] tempArrayNumbers = new int[arrayNumbers.Length + 1];

                        for (int i = 0; i < arrayNumbers.Length; i++)
                        {
                            tempArrayNumbers[i] = arrayNumbers[i];
                        }

                        tempArrayNumbers[tempArrayNumbers.Length - 1] = numberIput;
                        arrayNumbers = tempArrayNumbers;
                        break;
                }
            }