Serialize object without null field/member in .net web api

using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Runtime.Serialization;
using System.Web.Http;

namespace WebApplication1.Controllers
{
    public class MemberController : ApiController
    {
        // GET api/member/5
        public Member Get(int id)
        {
            return new Member()
            {
                ID = id,
                FirstName = "Bruce"
            };
        }
    }

    [DataContract]
    public class Member
    {
        [DataMember]
        public int ID { get; set; }
        [DataMember(EmitDefaultValue = false)]
        [JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
        public string FirstName { get; set; }
        [DataMember(EmitDefaultValue = false)]
        [JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
        public string LastName { get; set; }
        [DataMember(EmitDefaultValue = false)]
        [JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
        public DateTime? Birthday { get; set; }
    }
}