calcBigPrimeNumbers

using System;
using System.Diagnostics;
using System.Numerics;

public class Program
{
    public static void Main()
    {
        Console.WriteLine("     ==> Int");
        int[] numbers = { 50000017, 100000007 };
        for (int i = 0; i < numbers.Length; i++)
        {
            IsPrime(numbers[i]);
        }


        Console.WriteLine("     ==> BigInt");
        BigInteger[] big = { 50000017, 100000007 };
        for (int i = 0; i < big.Length; i++)
        {
            IsPrime(big[i]);
        }

        Console.WriteLine("     ==> Square BigInt <==");
        for (int i = 0; i < big.Length; i++)
        {
            BigIntegerPrime(big[i]);
        }

        BigInteger theNumber = 6737626471;
        BigIntegerPrime(theNumber);

        Console.WriteLine("\n   Press any key to the problem!");
        Console.ReadKey();

        InfinityLoop();
    }

    // int
    static void IsPrime(int num)
    {
        bool isPrime = true;
        var stopwatch = new Stopwatch();

        stopwatch.Start();
        for (int i = 2; i < num; i++)
        {
            if (num % i == 0)
            {
                Console.WriteLine(isPrime == false);
                break;
            }
        }
        var time = stopwatch.Elapsed;
        stopwatch.Stop();
        Console.WriteLine("number: {0}          {1} mil.", num, (num / 1000000));   //  nubmer / one milion
        Console.WriteLine("Prime?: {0}", isPrime);
        Console.WriteLine(time);
        Console.WriteLine();
    }

    // BigInt
    static void IsPrime(BigInteger num)
    {
        bool isPrime = true;
        var stopwatch = new Stopwatch();

        stopwatch.Start();
        for (BigInteger i = 2; i < num; i++)
        {
            if (num % i == 0)
            {
                Console.WriteLine(isPrime == false);
                break;
            }
        }
        var time = stopwatch.Elapsed;
        stopwatch.Stop();
        Console.WriteLine("number: {0}          {1} mil.", num, (num / 1000000));   //  nubmer / one milion
        Console.WriteLine("Prime?: {0}", isPrime);
        Console.WriteLine(time);
        Console.WriteLine();
    }

    // Square BigInt
    static void BigIntegerPrime(BigInteger num)
    {
        bool isPrime = true;
        var stopwatch = new Stopwatch();

        stopwatch.Start();
        for (BigInteger i = 2; i <= (BigInteger)Math.Sqrt((double)num); i++)
        {
            if (num % i == 0)
            {
                isPrime = false;
                Console.WriteLine(isPrime);
                break;
            }
        }
        var time = stopwatch.Elapsed;
        stopwatch.Stop();
        Console.WriteLine("number: {0}          {1} mil.", num, (num / 1000000));   //  nubmer / one milion
        Console.WriteLine("Prime?: {0}", isPrime);
        Console.WriteLine(time);
        Console.WriteLine();
    }

    // byte.MaxValue = 255.... byte.MinValue = 255 + 1 ??
    static void InfinityLoop()
    {
        bool isNewPoint = true;
        for (byte i = byte.MinValue; i < 300; i++)    // byte: 0-255 !!!    byte: 255++ == 0    i < 300.. infinity loop!
        {
            if (isNewPoint && i == byte.MaxValue)
            {
                Console.WriteLine("  i= {0} ==>  This is a new point!", i);
                System.Threading.Thread.Sleep(2000);
                isNewPoint = false;
            }
            else if (i == byte.MaxValue)
            {
                Console.WriteLine("  i= {0} ==>  I was here!", i);
                System.Threading.Thread.Sleep(2000);
            }
        }
    }
}