using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Runtime.Serialization.Formatters;

using System.IO;

using System.Data;

using System.ComponentModel.DataAnnotations;

using System.ComponentModel;

using System.Globalization;

using System.Reflection;

​

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

using Newtonsoft.Json.Converters;

using Newtonsoft.Json.Serialization;    

​

using NUnit.Framework; // Throws NUnit.Framework.AssertionException

​

//https://stackoverflow.com/questions/74446649/how-can-i-write-comment-from-attribute-before-the-property-name-when-serializing

​

using DescriptionAttribute = System.ComponentModel.DescriptionAttribute;

​

    public class DescriptionContractResolver : DefaultContractResolver

    {

        protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization memberSerialization)

        {

            IList<JsonProperty> props = base.CreateProperties(type, memberSerialization);

​

            foreach (var property in props)

            {

                if (property.Converter == null

                    && property.AttributeProvider.GetAttributes(typeof(System.ComponentModel.DescriptionAttribute), true) is {} array 

                    && array.Count > 0 

                    && ((System.ComponentModel.DescriptionAttribute)array[0]).Description is {} description)

                {

                    property.Converter = new CommentConverter(description);

                }

            }

​

            return props;

        }

    }

​

    class CommentConverter : JsonConverter

    {

        readonly string comment;

        public CommentConverter(string comment) => this.comment = comment ?? throw new ArgumentNullException(nameof(comment)); 

        public override bool CanConvert(Type objectType) => throw new NotImplementedException("This converter is should only be applied directly to properties.");

        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)

        {

            writer.WriteComment(comment);

            serializer.Serialize(writer, value);

        }

​

        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)

        {

            // Chew through comments for safety

            reader.MoveToContentAndAssert();

            return serializer.Deserialize(reader, objectType);

        }

    }

    public static partial class JsonExtensions

    {

        public static JsonReader MoveToContentAndAssert(this JsonReader reader)

        {

            if (reader == null)

                throw new ArgumentNullException();

            if (reader.TokenType == JsonToken.None)       // Skip past beginning of stream.

                reader.ReadAndAssert();

            while (reader.TokenType == JsonToken.Comment) // Skip past comments.

                reader.ReadAndAssert();

            return reader;

        }

​

        public static JsonReader ReadAndAssert(this JsonReader reader)

        {

            if (reader == null)

                throw new ArgumentNullException();

            if (!reader.Read())

                throw new JsonReaderException("Unexpected end of JSON stream.");

            return reader;

        }

    }

​

    public class DescriptionConfiguration

    {

        [Description("Last name of the human")]

        [DefaultValue("David")]

        public string LastName { get; set; }

​

        public DescriptionConfiguration()

        {

            // Use the DefaultValue property of each property to actually set it, via reflection.

            SetDefaultValues(this);

        }

​

        private void SetDefaultValues(object obj)

        {

            foreach (PropertyDescriptor prop in TypeDescriptor.GetProperties(obj))

            {

                DefaultValueAttribute attr = (DefaultValueAttribute) prop.Attributes[typeof(DefaultValueAttribute)];

                if (attr != null)

                {

                    prop.SetValue(obj, attr.Value);

                }

            }

        }

    }

​

    class TestClass

    {

        public static void Test()

        {

            var model = new DescriptionConfiguration();

            var resolver = new DescriptionContractResolver();  // Cache this statically for best performance

            var settings = new JsonSerializerSettings

            {

                ContractResolver = resolver,

            };

            var json = JsonConvert.SerializeObject(model, Formatting.Indented, settings);

            Console.WriteLine(json);

        }   

    }

​

    public class Program

    {

        public static void Main()

        {

            Console.WriteLine("Environment version: {0} ({1}), {2}", System.Runtime.InteropServices.RuntimeInformation.FrameworkDescription , Environment.Version, Environment.OSVersion);

            Console.WriteLine("{0} version: {1}", typeof(JsonSerializer).Namespace, typeof(JsonSerializer).Assembly.FullName);

            Console.WriteLine();

​

            try

            {

                TestClass.Test();

            }

            catch (Exception ex)

            {

                Console.WriteLine("Failed with unhandled exception: ");

                Console.WriteLine(ex);

                throw;

            }

        }

    }

​