using System;

​

public class Program

{

    public static void Main()

    {

        var a = new TestObject();

        var output = $"{(a?.Foo?.BarOb?.SayA) ?? "I'm the default for a null value"}";

        Console.WriteLine(output);

    }

​

    public class FooObject

    {

        public BarObject BarOb

        {

            get;

            set;

        }

    }

​

    public class BarObject

    {

        public string SayA

        {

            get;

            set;

        }

​

        public string SayB

        {

            get;

            set;

        }

    }

​

    public class TestObject

    {

        public FooObject Foo

        {

            get;

            set;

        }

    }

}