using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    static event EventHandler MyEvent;

​

    public static void Main()

    {

        List<string> testList = new List<string>();

        testList.Add("test1");

        testList.Add("test2");

        string test = testList.SingleOrDefault();

        if(test == null){

            Console.WriteLine("NULL");

        } else {

            Console.WriteLine("NOT NULL");

        }

    }

}