using System;

using Newtonsoft.Json;

using System.ComponentModel;

public class Invoice

{

    [JsonProperty(DefaultValueHandling = DefaultValueHandling.Populate)]

    [DefaultValue("Company")]

    public string Company { get; set; }

    public decimal Amount { get; set; }

​

    // false is default value of bool

    public bool Paid { get; set; }

    // null is default value of nullable

    public DateTime? PaidDate { get; set; }

​

    // customize default values

    [DefaultValue(30)]

    [JsonProperty(DefaultValueHandling = DefaultValueHandling.Populate)]

    public int FollowUpDays { get; set; }

​

    [DefaultValue("")]

    public string FollowUpEmailAddress { get; set; }

}

​

public class Program

{

    public static void Main()

    {       

        Invoice invoice = new Invoice

        {

            Company = "Acme Ltd.",

            Amount = 50.0m,

            Paid = false,

            FollowUpDays = 30,

            FollowUpEmailAddress = string.Empty,

            PaidDate = null

        };

​

        string included = JsonConvert.SerializeObject(invoice, Formatting.Indented, new JsonSerializerSettings { });

        Console.WriteLine(included);

        Console.WriteLine("");

        string raw = "{ \"Company1\": \"Acme Ltd.\", \"Amount\": 50.0, \"Paid\": false, \"PaidDate\": null, \"FollowUpDays\": 30, \"FollowUpEmailAddress\": \"\" }";

        string ignored = JsonConvert.SerializeObject(invoice, Formatting.Indented, new JsonSerializerSettings { DefaultValueHandling = DefaultValueHandling.Ignore });

        Console.WriteLine(ignored);     

        var settings = new JsonSerializerSettings();

        settings.NullValueHandling = NullValueHandling.Ignore;

        var myObj = JsonConvert.DeserializeObject<Invoice>(raw, settings);

        Console.WriteLine(myObj.Company ?? "null");

    }

}