using System;

using System.Linq.Expressions;

​

using System.Collections.Generic;

​

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

using Newtonsoft.Json.Serialization;

​

public class Program

{

    public static void Main()

    {

        var settings = new JsonSerializerSettings

        {

            Formatting = Formatting.None,           

            ContractResolver = new CamelCasePropertyNamesContractResolver()

        };

        var test = new Test();

        test.PropertyA = "foo";

        Console.WriteLine(JsonConvert.SerializeObject(test, settings));

        Console.WriteLine(JObject.FromObject(test, JsonSerializer.Create(settings)).ToString(Formatting.None));

    }

}

​

public class Test

{

    private string _propertyA;

    public string PropertyA

    {

        get => _propertyA;

        set

        {

            ChangedProperties.Add(nameof(PropertyA));

            _propertyA = value;

        }           

    }

    [JsonIgnore]

    public ISet<string> ChangedProperties {get;} = new HashSet<string>();

}