using System;

public class Program

{

    class A

    {

        public bool IsEnabled;  

    };

    public static void Main()

    {

        var a = new A { IsEnabled = true };

        Console.WriteLine("IsEnabled = true");

​

        if(a.IsEnabled != true)

        {

            Console.WriteLine("A -- feature disabled, return null");

        }

        else

        {

            Console.WriteLine("B -- feature enabled");

        }

        Console.WriteLine("class is null");

        a = null;

​

        if(a?.IsEnabled != true)

        {

            Console.WriteLine("A -- feature disabled, return null");

        }

        else

        {

            Console.WriteLine("B -- feature enabled");

        }

    }

}