Prime Number Formula

Question

I am trying to write a prime number function in C# and I am wondering if the follow code will work. It \"appears\" to work with the first 50 numbers or so. I just want to ma

Answer 1

    static List PrimeNumbers = new List();

    static void Main(string[] args)
    {
        PrimeNumbers.Add(2);
        PrimeNumbers.Add(3);
        PrimeNumbers.Add(5);
        PrimeNumbers.Add(7);
        for (long i = 11; i < 10000000; i += 2)
        {
            if (i % 5 != 0)
                if (IsPrime(i))
                    PrimeNumbers.Add(i);
        }
    }

    static bool IsPrime(long number)
    {
        foreach (long i in PrimeNumbers)
        {
            if (i <= Math.Sqrt(number))
            {
                if (number % i == 0)
                    return false;
            }
            else
                break;
        }
        return true;
    }