Twin Prime Numbers Within A Range In C#

namespace Consolepractice {
    class Program {
        public static void Main(string[] args) {
            Program pg = new Program();
            for (int i = 2; i <= 200; i++) {
                if (pg.checkprime(i) == true && pg.checkprime(i + 2) == true) {
                    Console.WriteLine(i + "," + (i + 2));
                }
            }
            Console.ReadKey();
        }
        public bool checkprime(int n) {
            int flag = 0;
            for (int i = 2; i <= n / 2; i++) {
                if (n % i == 0) {
                    flag = 1;
                    break;
                }
            }
            if (flag == 0) {
                return true;
            } else {
                return false;
            }
        }
    }
}