using System;

using Newtonsoft.Json;

public class Program

{

    public static void Main()

    {

        try

        {

            Console.WriteLine("Try serialize");

            var testObject = new TestObject("SomeValue");

            var testObjectJson = JsonConvert.SerializeObject(testObject);

            Console.WriteLine($"Serialized object: '{testObjectJson}'");

            Console.WriteLine();

            Console.WriteLine("Try serialize null");

            var testObject2 = new TestObject(null);

            var testObject2Json = JsonConvert.SerializeObject(testObject2);

            Console.WriteLine($"Serialized object: '{testObject2Json}'");

        }

        catch (Exception ex)

        {

            Console.WriteLine(ex);

        }

    }

}

​

[JsonObject(MemberSerialization = MemberSerialization.OptIn)]

class TestObject

{

    [JsonProperty(Required = Required.Always)]

    public string SomeProperty { get; }

    public TestObject(string someProperty)

    {

        SomeProperty = someProperty;

    }

}