using Newtonsoft.Json;
using System;namespace Hitearth
{class Hitearth{static void Main(string[] args){var demos = new[]{new demo { attr1 = "11", attr2 = "12",attr3 = "13" },new demo { attr1 = "21", attr2 = "22",attr3 = "23" },};var demo2 = new demo();demo2.obj = demo2;var demo3 = new demo { attr2 = "demo3" };demo3.obj = new demo { attr2 = "demo3.obj", obj = new demo { attr2 = "demo3.obj.obj" } };Console.WriteLine(JsonConvert.SerializeObject(demos));  // [{"attr1":"11","attr2":"12","attr3":"13","obj":null},{"attr1":"21","attr2":"22","attr3":"23","obj":null}]test(demos, "attr1 attr2".Split(' ')); // [{"attr1":"11","attr2":"12"},{"attr1":"21","attr2":"22"}]test(demos, "attr2 attr3".Split(' ')); // [{"attr2":"12","attr3":"13"},{"attr2":"22","attr3":"23"}]test(demos, new string[] { }); // [{},{}]test(demo2, "attr2 attr3".Split(' '));  // {"attr2":null,"attr3":null}test(demo2, "attr2 obj".Split(' '));  // Self referencing loop detected with type 'Hitearth.demo'.Path ''.test(demo3, "attr2 obj".Split(' '));// {"attr2":"demo3","obj":{"attr2":"demo3.obj","obj":{"attr2":"demo3.obj.obj","obj":null}}}}static void test(object obj, string[] attrs){try{Console.WriteLine(JsonConvert.SerializeObject(obj, new FilterPropertiesJsonConverter(typeof(demo), attrs)));}catch (Exception ex){Console.WriteLine(ex.Message);}}}public class demo{public string attr1 { get; set; }public string attr2 { get; set; }public string attr3 { get; set; }public demo obj { get; set; }}}

using Newtonsoft.Json;
using Newtonsoft.Json.Serialization;
using System;
using System.Linq;namespace Hitearth
{/// <summary>/// 只序列化 jsonProperties 指定的字段/// </summary>/// <typeparam name="T"></typeparam>public class FilterPropertiesJsonConverter : JsonConverter{Type type; string[] jsonProperties; bool reversed = false;public FilterPropertiesJsonConverter(Type type, string[] jsonProperties, bool reversed = false){if (type == null) throw new ArgumentNullException("type");if (jsonProperties == null) throw new ArgumentNullException("jsonProperties");this.type = type;this.jsonProperties = jsonProperties;this.reversed = reversed;}public override bool CanConvert(Type objectType){return objectType == type;}public override bool CanRead { get { return false; } }public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer) { throw new NotImplementedException(); }public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer){if (value == null){writer.WriteNull();return;}var contract = serializer.ContractResolver.ResolveContract(value.GetType()) as JsonObjectContract;writer.WriteStartObject();if (contract != null){foreach (var item in contract.Properties){if (jsonProperties.Contains(item.PropertyName) == reversed)continue;writer.WritePropertyName(item.PropertyName);serializer.Serialize(writer, item.ValueProvider.GetValue(value));}}writer.WriteEndObject();}}
}