prime no

Hi

I have same problem.Thanks for this code it will help me to solve the issue of  prime no.

that does sound like the way to go (BigInt).  Alsoc check out
http://www.fractal-landscapes.co.uk/bigint.html

In .net 4 you have new class called BigInteger and it is in namespace System.Numerics(first you need to add this namespace using AddReference dialog),
and you can't use Math.Pow() because it return's long and we need BigInteger so we need our Function for potentiation and that function should look like this:
       private BigInteger BetterPow(int x, int y)
        {
            BigInteger res=x;

            for (int i = 1; i < y; i++)
            {
                res*=x;
            }

            return res;
        }

EDIT!!!

And you code should look like this:
bool prime = false;
            Console.WriteLine((BetterPow(2, 511)).ToString());
            Console.WriteLine((BetterPow(2, 512)).ToString());
            BigInteger a = BetterPow(2, 511);
            BigInteger b = BetterPow(2, 512);
            Console.WriteLine((b - a).ToString());
            Console.WriteLine("");

            //This is remainder what lefd dividing two BigIneger numbers(in BigInteger % operator isn't implemented)
            BigInteger remainder;
            for (BigInteger number = a; number < b; number++)
            {
                for (BigInteger divisor = 2; divisor < a; )
                {
                    remainder = BigInteger.Remainder(number, divisor);
                    if (BigInteger.Compare(remainder, 0) == 0)
                    {
                        prime = false;
                        break;
                    }
                    else
                    {
                        prime = true;
                        break;
                    }
                }

                if (prime)
                {
                    Console.WriteLine(number.ToString());
                }

            }

            Console.ReadLine();

 
BTW.  I put source so if download and try it.

Also check out the following http://en.wikipedia.org/wiki/Primality_test.  This may guide you a little bit and give you some ideas.

that problem does not sound easy to me, but I suspect you would do it with a set of 8 long values (or 8 64 bit values)  representing each number.  You can't do it with doubles (e.g. Math.Pow) because you'll get rounding errors in the higher numbers)
 
-Mike