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

namespace ConsoleApplication1
{
    class TClass
    {
        public int Num;
    }
    class Program
    {
        static void Main(string[] args)
        {
            TClass obj = new TClass();
            obj.Num = 10;
            List<TClass> array1 = new List<TClass>();
            array1.Add(obj);
            List<TClass> list2 = array1;
            obj.Num = 20;
            Console.WriteLine(list2[0].Num);
            Console.ReadKey(false);
        }
    }
}