PrimeNumber

using System;

namespace PrimeNumber
{
    class PrimeNumber
    {
        static void Main()
        {
            int number;
            Console.WriteLine("Enter a random number to check if it's prime:");
            number = Convert.ToInt32(Console.ReadLine());
            int forCaseSt;
            Console.WriteLine("Choose an algorithm for checking the number (1 for SQRT, 2 for HALF).");
            forCaseSt = Convert.ToInt32(Console.ReadLine());
            if (forCaseSt == 1)
            {
                double numberSqrt = Math.Sqrt(number);
                int numberSqrtRound = (int)Math.Round(numberSqrt);
                if (number == 0 || number == 1)
                {
                    Console.WriteLine(number + " is not a prime number");
                }
                else
                {
                    for (int i = 2; i <= numberSqrtRound; i++)
                    {
                        if (number % i == 0)
                        {
                            Console.WriteLine(number + " is not a prime number.");
                            return;
                        }
                    }
                    Console.WriteLine(number + " is a prime number.");
                }
            }
            else if (forCaseSt == 2)
            {
                double numberHalf = (double)(number / 2);
                int numberHalfRound = (int)Math.Round(numberHalf);

                if (number == 0 || number == 1)
                {
                    Console.WriteLine(number + " is not a prime number");
                }
                else
                {
                    for (int i = 2; i <= numberHalfRound; i++)
                    {
                        if (number % i == 0)
                        {
                            Console.WriteLine(number + " is not a prime number");
                            return;
                        }
                    }
                    Console.WriteLine(number + " is a prime number");
                }
            }
        }
    }
}