Primes in Range

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

class PrimesInRange
{
    static List<int> FindPrimes(int startNum, int endNum)
    {
        List<int> primesCollection = new List<int>();

        if (startNum < 2)
        {
            startNum = 2;
        }

        for (int i = startNum; i <= endNum; i++)
        {
            int divider = 2;
            double maxDivider = Math.Sqrt(i);
            bool isPrime = true;

            while (divider <= maxDivider)
            {
                if (i % divider == 0)
                {
                    isPrime = false;
                    break;
                }

                divider++;
            }

            if (isPrime)
            {
                primesCollection.Add(i);
            }
        }

        return primesCollection;
    }

    static void Main()
    {
        int startNum = int.Parse(Console.ReadLine());
        int endNum = int.Parse(Console.ReadLine());

        if (startNum > endNum)
        {
            Console.WriteLine("(empty list)");
        }
        else
        {
            List<int> primes = FindPrimes(startNum, endNum);

            for (int i = 0; i < primes.Count; i++)
            {
                if (i < primes.Count - 1)
                {
                    Console.Write(primes[i] + ", ");
                }
                else
                {
                    Console.WriteLine(primes[i]);
                }
            }
        }
    }
}