c#程序冻结整数列表

当我运行我的程序时,我会初始化一个整数列表并冻结.我知道这是因为Console.WriteLine();列表初始化后的方法不会出现在控制台上.当我运行它时,唯一的输出是“在列表之前”.我错过了什么？我真的希望这不是很明显和令人尴尬.

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

namespace Euler._1_50
{
    class ChALLENge3
    {
        public ChALLENge3()
        {
            Console.WriteLine("before list");

            long num = 600_851_475_143;
            long high = 0;
            long length = 0;
            List<int> factr = new List<int>();

            Console.WriteLine(IsPrime(num));
            Console.WriteLine("after list");

            for (long i = 2; i <= num / 2; i++)
            {
                if (IsPrime(i) && num / i == 0)
                {
                    num = num / i;
                    factr.Add((int)i);
                    length++;
                }
            }

            for (long i = 0; i <= length; i++)
            {
                if (i > high) high = i;
            }

            Console.WriteLine(high);

        }

        private bool IsPrime(long i)
        {
            bool isPrime = false;

            for (long j = 2; j <= i/2; j++)
            {
                if (i % j == 0) isPrime = false;
                else isPrime = true;
            }
            return isPrime;
        }
    }
}

private bool IsPrime(long i)
{
    long upper = (long)Math.Sqrt(i);
    for (long j = 2; j <= upper; j++)
    {
        if (i % j == 0)
           return false;
    }
    return true;
}