Check Whether a Number is Prime or Not Using C# Language

using System;

namespace String
{
    class Prime
    {

        static void Main(string[] args)
        {
            int count = 0;
            Console.WriteLine("Enter a num");
            int a = Convert.ToInt32(Console.ReadLine());
            for (int i = 1; i <= (a / 2); i++)
            {
                if (a % i == 0)
                {
                    count++;
                }
            }
            if (count == 1)
            {
                    Console.WriteLine(" Prime number");
                }
            else
            {
                Console.WriteLine(" Is not Prime number");
            }
            Console.ReadLine();
        }
    }
}