using System;

using System.Collections.Generic;

​

namespace ConsoleApp1

{   

    public class MyClass<T>{

        public readonly int num;

        public MyClass(List<T> list){

            num=list.Count;

        }

    }

    public class Program

    {

        public static void Main()

        {

            var instance = new MyClass<int>(new List<int>{1,3});

            var p = instance.num;

            Console.WriteLine(p);

        }

    }

}

​