using System;

using System.Collections.Generic;

using System.Threading.Tasks;

using System.Linq;

​

public class Program

{

    public class IsolationDomain

    {

        public External External {get;set;} //= new External();

    }

    public class External

    {

        public string Name {get;set;} = "Child";

        public List<GrandChild> GrandChilds {get; set;} //= new List<GrandChild>() { new GrandChild{ } };

    }

    public class GrandChild

    {

        public string Name {get;set;} = "Grand Child";

    }

    public static void Main()

    {   

        IsolationDomain parent10 = new IsolationDomain();

        Console.WriteLine("Count {0}", parent10?.External?.GrandChilds?.Count ?? 0);

        Console.WriteLine("Has any items: {0}", parent10?.External?.GrandChilds?.Count != 0);

        Console.WriteLine("Has any items: {0}", parent10?.External?.GrandChilds?.Count > 0);

    }

}