Task Collection 3

const string InputSumNumbers = "sum";
const string ExitProgram = "exit";

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

while (isWork == true)
{
    string input = Console.ReadLine();

    switch (input)
    {
        case InputSumNumbers:
            SumNumbers(numbers);
            break;

        case ExitProgram:
            isWork = false;
            break;

        default:
            AddNumbers(input, numbers);
            break;
    }
}

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

    foreach (int number in inputNumbers)
    {
        sum += number;
    }
    Console.WriteLine($"Сумма всех чисел ровна {sum}");
}

static void AddNumbers(string userInput, List<int> inputNumbers)
{
    bool isNumber = int.TryParse(userInput, out int number);

    if (isNumber == true)
    {
        inputNumbers.Add(number);
    }
    else
    {
        Console.WriteLine("\nНекорректный ввод\n");
    }
}