using System;

using System.Net.Http;

using System.Threading.Tasks;

public class Program

{

    public static async Task Main()

    {

        var testOptions = new TestOptions();

        testOptions.GetMessageId = () => "Test";

        var testOptions2 = new TestOptions();

        Console.WriteLine(testOptions.GetMessageId());

        if(testOptions2.GetMessageId != null)

            Console.WriteLine(testOptions2.GetMessageId());

    }

    public class TestOptions

    {

        public Func<string> GetMessageId { get; set; }

    }

}