Prime Sum

Problem 10 Project Euler 

The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17.

Find the sum of all the primes below two million.

Prime Check Snippet

static bool IsPrime(int n)
        {
            if (n == 2 || n == 3)
                return true;

            if (n < = 1 || n % 2 == 0 || n % 3 == 0)
                return false;

            for (int i = 5; i * i < = n; i += 6)
            {
                if (n % i == 0 || n % (i + 2) == 0)
                    return false;
            }

            return true;
        }

Full Code Snippet

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
class Solution {

    static void Main(String[] args) {
        int t = Convert.ToInt32(Console.ReadLine());
        for(int a0 = 0; a0 < t; a0++){
            int n = Convert.ToInt32(Console.ReadLine());
            Console.WriteLine(PrimeSum(n));
        }
    }
    static long PrimeSum(int n)
        {
            long sum = 2;
            if (n == 2) return 2;

            for (var i = 3; i < = n; i+=2)
            {
                if (IsPrime(i))
                {
                    sum += i;
                }
            }
            return sum;
        }
        static bool IsPrime(int n)
        {
            if (n == 2 || n == 3)
                return true;

            if (n < = 1 || n % 2 == 0 || n % 3 == 0)
                return false;

            for (int i = 5; i * i < = n; i += 6)
            {
                if (n % i == 0 || n % (i + 2) == 0)
                    return false;
            }

            return true;
        }
}

Live Code On Ide One