using System;

using System.Collections.Generic;

public class Program

{

    //private static List<string> temps = new List<string>();

    public static void Main()

    {

        for (int i = 0; i <= 2; i++)

        {

            while (true)

            {

                Foo(ref List<string> temps);

​

                if (temps != null)

                {

                    Console.WriteLine("add");

                    break;

                }

                else

                {

                    Console.WriteLine("null");

                    break;

                }

            }

        }

        //Console.WriteLine(temps.Count);

    }

    private static void Foo (ref List<string> temp)

    {

        Random rnd = new Random();

        bool flag = 0 == rnd.Next(0, 2) ? true : false;

        Console.WriteLine(flag);

        if (flag)

            temp = null;

        else

            temp = new List<string>(){"1", "2"};

    }

}