using System;

public class Program

{

    public static void Main()

    {

        var d = new Test() { 

        };

        Console.WriteLine(d.a?.x.y);

    }

}

​

public class Test { 

    public TestTwo a;   

}

public class TestTwo {

    public TestThree x;

}

public class TestThree {

    public long y;

}