using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

​

namespace ConsoleApp1

{

    public class Program

    {

        public static void Main(string[] args)

        {

            List<int> list = GetNumbers().ToList();

​

            foreach (var item in list)

            {

                Console.Write(item + "; ");

            }

​

            Console.WriteLine();

​

            IEnumerable enumerable = GetNumbers();

​

            if (!enumerable.IsEmpty())

            {

                foreach (var item in enumerable)

                {

                    Console.Write(item + "; ");

                }

            }

        }

​

        private static IEnumerable<int> GetNumbers()

        {

            int i = 0;

​

            while (i < 10)

            {

                yield return i++;

            }

        }

    }

​

    public static class EnumerableExtensions

    {

        public static bool IsEmpty(this IEnumerable source)

        {

            foreach (var item in source)

            {

                return false;

            }

​

            return true;

        }

    }

}

​