using System;

using System.Text.RegularExpressions;

using Newtonsoft.Json;

using Newtonsoft.Json.Converters;

public class Program

{

    public static void Main()

    {

        string json = JsonConvert.SerializeObject(new SimpleClassWithRegex { RegProp = null }, Formatting.Indented);

        Console.WriteLine(json);

        SimpleClassWithRegex obj = JsonConvert.DeserializeObject<SimpleClassWithRegex>(json, new ImprovedRegexConverter());

    }

}

​

public class SimpleClassWithRegex

{

    public Regex RegProp { get; set; }

}

​

public class ImprovedRegexConverter : RegexConverter

{

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

    {

        if (reader.TokenType == JsonToken.Null)

        {

            return null;

        }

        return base.ReadJson(reader, objectType, existingValue, serializer);

    }

}

​