using System;

using System.Linq;              

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        var p = new Program();

        var list = p.CreateEnumerable<int?>(1, 2, 3, 4);

        p.DoWork(list);

    }

​

    public void DoWork(IEnumerable<int?> enumerable)

    {

        enumerable.ToList().ForEach(x => 

        {

            Console.WriteLine(x);

        });

    }

    public IEnumerable<T> CreateEnumerable<T>(params T[] items)

    {

        if (items == null)

            yield break;

​

        foreach (T mitem in items)

            yield return mitem;

    }

}