using System;

using System.Collections.Generic;

using Newtonsoft.Json;

using System.Reflection;

​

​

public class Program

{

    public static void Main()

    {

        var settings = new JsonSerializerSettings

        {

            Converters = new[] { new ValueTypeConverter() },

            Formatting = Newtonsoft.Json.Formatting.Indented

        };

        string json = JsonConvert.SerializeObject(

            new TestClass

            {

                Date = DateTime.MinValue,

                Integer = int.MinValue,

                Double = 4.0d,

                Short = 10

            }, settings);

        Console.WriteLine(json);

        var test = JsonConvert.DeserializeObject<TestClass>(json, settings);

        test.Dump();

    }

    public class TestClass

    {

        public DateTime Date { get; set; }

        public short Short { get; set; }

        public double Double { get; set; }

        public int Integer { get; set; }

    }   

    public class ValueTypeConverter : JsonConverter

    {

        private static List<Type> SupportedTypes = new List<Type>

        {

            typeof(short),

            typeof(int),

            typeof(long),

            typeof(float),

            typeof(double),

            typeof(decimal),

            typeof(DateTime)

        };

        private static Dictionary<Type, object> MinValues;

        static ValueTypeConverter()

        {

            MinValues = new Dictionary<Type, object>();

            foreach (Type type in SupportedTypes)

            {

                MinValues.Add(type, GetMinValue(type));

            }

        }

        public override object ReadJson(

            JsonReader reader, 

            Type objectType,

            object existingValue,

            JsonSerializer serializer)

        {

            object value = reader.Value;

            value = value ?? MinValues[objectType];

            value = Convert.ChangeType(value, objectType);

            return value;

        }

        public override bool CanConvert(Type objectType)

        {

            return MinValues.ContainsKey(objectType);

        }

        public override void WriteJson(

            JsonWriter writer, object value, JsonSerializer serializer)

        {        

            object minValue = MinValues[value.GetType()];

            if (object.Equals(value, minValue))

            {

                value = null;

            }

            writer.WriteValue(value);

        }

        private static object GetMinValue(Type objectType)

        {

            FieldInfo minValueFieldInfo = objectType.GetField("MinValue");

            return minValueFieldInfo.GetValue(null);

        }

    }   

}