using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public string Name { get; set; }

    public static void Main()

    {

        List<Program> list = new List<Program>() {};

        //Console.WriteLine(list.FirstOrDefault().Name); // Run-time exception (line 13): Object reference not set to an instance of an object.

        //Console.WriteLine(list.First().Name); // Run-time exception (line 14): Sequence contains no elements

        //Console.WriteLine(list.Single().Name); // Run-time exception (line 15): Sequence contains no elements

        //Console.WriteLine(list.SingleOrDefault().Name); // Run-time exception (line 16): Object reference not set to an instance of an object.

    }

}