using System;

using System.Linq;

using System.Text.Encodings;

using System.Linq;

using System.Collections.Generic;

public class Program

{

        public class InnerClass {

            public int number { get; set; }

        }

        public class OuterClass {

            public InnerClass innerClass {get; set;}

        }

​

    public static void Main()

    {

        var myOuterClass = new OuterClass();

        if(myOuterClass.innerClass != null)

            Console.WriteLine("is not null");

        else

            Console.WriteLine("is null");

​

    }

}