【答客問】Json.NET-動態決定屬性是否序列化

using System;

using System.Collections.Generic;

using System.Linq;

using System.Reflection;

using System.Text;

using Newtonsoft.Json;

using Newtonsoft.Json.Converters;

using Newtonsoft.Json.Serialization;

namespace ConsoleApplication1

{

    class Program

    {

        public enum Gender 

        {

            Male, Female

        }

        public class Person

        {

            public string Name { get; set; }

            [JsonConverter(typeof(StringEnumConverter))]

            public Gender Gender { get; set; }

            public int Age { get; set; }

            public Person(string name, Gender gender, int age)

            {

                Name = name; Gender = gender; Age = age;

            }

        }

        public class HideAgeContractResolver : DefaultContractResolver

        {

            //REF: http://james.newtonking.com/projects/json/help/index.html?topic=html/ContractResolver.htm

            protected override JsonProperty CreateProperty(MemberInfo member, 

                MemberSerialization memberSerialization)

            {

                JsonProperty p = base.CreateProperty(member, memberSerialization);

                if (p.PropertyName == "Age")

                {

                    //依性別決定是否要序列化

                    p.ShouldSerialize = instance =>

                    {

                        Person person = (Person)instance;

                        return person.Gender == Gender.Male;

                    };

                }

                return p;

            }

        }

        public class LimitPropsContractResolver : DefaultContractResolver

        {

            string[] props = null;

            public LimitPropsContractResolver(string[] props)

            {

                //指定要序列化屬性的清單

                this.props = props;

            }

            //REF: http://james.newtonking.com/archive/2009/10/23/efficient-json-with-json-net-reducing-serialized-json-size.aspx

            protected override IList<JsonProperty> CreateProperties(Type type, 

                MemberSerialization memberSerialization)

            {

                IList<JsonProperty> list = 

                    base.CreateProperties(type, memberSerialization);

                //只保留清單有列出的屬性

                return list.Where(p => props.Contains(p.PropertyName)).ToList();

            }

        }

        static void Main(string[] args)

        {

            List<Person> list = new List<Person>();

            list.Add(new Person("George", Gender.Male, 18));

            list.Add(new Person("Mary", Gender.Female, 40));

            //正常輸出

            Console.WriteLine(JsonConvert.SerializeObject(

                list, Formatting.Indented));

            var settings = new JsonSerializerSettings();

            //加上ContractResolver，正向表列哪些屬性要序列化

            settings.ContractResolver = 

                new LimitPropsContractResolver("Name,Age".Split(','));

            Console.WriteLine(JsonConvert.SerializeObject(

                list, Formatting.Indented, settings));

            //加上ContractResolver，依物件的屬性值動態決定要不要序列化

            settings.ContractResolver = new HideAgeContractResolver();

            Console.WriteLine(JsonConvert.SerializeObject(

                list, Formatting.Indented, settings));

            Console.ReadLine();

        }

    }

}