Answer by Steve for Continue loop between classes after wrong input

You could use the same pattern used by Int32.TryParse. Meaning you pass the number to be added as an out parameter and return a boolean false if the number is not valid

public static bool ReadIntegerConsole2(out int number)
{
    int input;
    bool ok = true;

    number = 0;
    if (int.TryParse(Console.ReadLine(), out input))
        number = input;
    else
    {
        ok = false;
        Console.WriteLine("Wrong input. Please try again: ");
    }
    return ok;
}

Now in the calling code you can control the loop knowing the result of the call to ReadInteger2

private void SumNumbers() 
{
    int index;
    int num = 0;
    for (index = 1; index <= numOfInput; index++) 
    {
        Console.Write("Please give the value no. " + index + " (whole number):");
        if(Input.ReadIntegerConsole2(out num))
            sum += num;
        else 
            // Decrement the counter to avoid skipping an input
            index--;
    }
}