using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var a1 = new List<int>();

        var b1 = Get(a1);

        a1.Add(1);

        Console.WriteLine(b1.Count());

        var a2 = new List<int>();

        var b2 = Get2(a2);

        a2.Add(1);

        Console.WriteLine(b2.Count());

    }

    public static IEnumerable<int> Get(IEnumerable<int>? ids)

    {

        return ids?.Any() == true ? ids : Enumerable.Empty<int>();

    }

    public static IEnumerable<int> Get2(IEnumerable<int>? ids)

    {

        return ids ?? Enumerable.Empty<int>();

    }

}