using System;

using System.Collections.Generic;

using System.Linq;

public static class EnumerableExtensions

    {

        public static IEnumerable<T> OrEmptyIfNull<T>(this IEnumerable<T> source)

        {

            return source ?? Enumerable.Empty<T>();

        }

    }

​

​

public class TestList

{

    public List<int> TestChild {get; set;}

}

​

public class Program

{

    public static void Main()

    {

        var testList = new TestList();

        var x = testList?.TestChild.OrEmptyIfNull();

​

        Console.Write(x == null);

    }

}