using System;

using System.Linq;

using System.Threading;

using System.Threading.Tasks;

using System.Collections.Generic;

​

public class Program

{

    public static async Task Main()

    {

        var resultNull = new Result();

        Validate(resultNull);

        var resultWithDataNull = new Result{Data = new[]{new Additional{AdditionalData = ""}}};

        Validate(resultWithDataNull);

        var resultWithDataAndAdditionalDataNull = new Result{Data = new[]{new Additional{AdditionalData = "test"}}};

        Validate(resultWithDataAndAdditionalDataNull);

    }

​

    private static void Validate(Result result)

    {

        if (result?.Data != null && result.Data.Any())

        {

            /// Expecting 'AdditionalData' is `string`

            if (!string.IsNullOrEmpty(result.Data.ElementAtOrDefault(0)?.AdditionalData))

            {

                Console.WriteLine("Null check working...");

            }

            else

            {

                Console.WriteLine("AdditionalData is null or empty!");

            }

        }

        else

        {

            Console.WriteLine("No data!");

        }

    }

​

    class Result

    {

        public IEnumerable<Additional> Data { get; set; }

    }

​

    class Additional

    {

        public string AdditionalData { get; set; }

    }

}