using System;

​

#nullable enable

public class Program

{

    // A class is a reference type

    public class Key

    {

        public ReadOnlyMemory<byte> ToEncoded()

        {

            return new byte[] { 1, 2, 3, 4 };

        }

    }

    public static void Main()

    {

        // a should be `null`

        Key? a = CreateKey(false);

        DoThing(a?.ToEncoded());

        // b should be instance of `Key`

        Key? b = CreateKey(true);

        DoThing(b?.ToEncoded());

        // try null directly

        DoThing(null);

    }

    public static Key? CreateKey(bool actuallyCreate)

    {

        return actuallyCreate ? new Key() : null;

    }

    public static void DoThing(ReadOnlyMemory<byte>? data, bool isEncoded = false)

    {

        Console.WriteLine($"Data HasValue = {data.HasValue} and isEncoded = {isEncoded}");

        if (data.HasValue)

        {

            Console.WriteLine(data.Value.Length);   

        }

    }

}