using System;

​

public class Program

{

    public static void Main()

    {

        var obj = new Foo{Bar = "bar", Barbarian = "AA_Sprzedam_Opla"};

        var json = Newtonsoft.Json.JsonConvert.SerializeObject(obj);

        Console.WriteLine(json);

        var serializerSettings = new Newtonsoft.Json.JsonSerializerSettings();

        serializerSettings.ContractResolver = new Newtonsoft.Json.Serialization.CamelCasePropertyNamesContractResolver();

        json = Newtonsoft.Json.JsonConvert.SerializeObject(obj, serializerSettings);

        Console.WriteLine(json);

    }

    public class Foo

    {

        public string Bar { get; set; }

​

        public string Barbarian { get; set; }

    }

}