using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Calling GetNums()");

        var a = GetNums();

        Console.WriteLine("Calling GetNums().ToList()");

        var b = GetNums().ToList();

    }

    public static IEnumerable<int> GetNums() {

        Console.WriteLine("GetNums() begin");

        yield return 1;

        Console.WriteLine("GetNums() returned 1");

        yield return 2;

        Console.WriteLine("GetNums() returned 2");

    }

}