Json.NET does not store primitive type information in object lists or dictionaries. Is there a workaround?

Question

The following example illustrates the fundamental drawback of handling Json.NET type types:

List<object> items = new List<object>() {Guid.NewGuid(),DateTime.Now}; var settings = new JsonSerializerSettings() { TypeNameHandling=TypeNameHandling.All }; var json = JsonConvert.SerializeObject<List<object>>(value,settings); 

which leads to the following JSON:

 {"$type":"System.Collections.Generic.List`1[[System.Object, mscorlib]], mscorlib","$values":["9d7aa4d3-a340-4cee-baa8-6af0582b8acd","2014-07-28T21:03:17.1287029-04:00"]} 

As you can see, the list items have lost type information. Deserializing the same JSON will result in a list containing only strings.

This issue was previously reported by Codeplex and completely closed, stating, including type information, which would make JSON too confusing. I am surprised that we are not given a separate option to include information about the primitive type for such scenarios when there is a violation of consistency in a circle.

https://json.codeplex.com/workitem/23833

I would expect the data to return with the same type information with which it was left. Does anyone have any suggestions or workarounds to eliminate this unwanted behavior?

Thanks,

Chris

Answer 1

Here is a solution using custom JsonConverter :

 public sealed class PrimitiveJsonConverter : JsonConverter { public PrimitiveJsonConverter() { } public override bool CanRead { get { return false; } } public override bool CanConvert(Type objectType) { return objectType.IsPrimitive; } 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) { switch (serializer.TypeNameHandling) { case TypeNameHandling.All: writer.WriteStartObject(); writer.WritePropertyName("$type", false); switch (serializer.TypeNameAssemblyFormat) { case FormatterAssemblyStyle.Full: writer.WriteValue(value.GetType().AssemblyQualifiedName); break; default: writer.WriteValue(value.GetType().FullName); break; } writer.WritePropertyName("$value", false); writer.WriteValue(value); writer.WriteEndObject(); break; default: writer.WriteValue(value); break; } } } 

Here's how to use it:

 JsonSerializerSettings settings = new JsonSerializerSettings() { TypeNameHandling = TypeNameHandling.All, }; settings.Converters.Insert(0, new PrimitiveJsonConverter()); return JsonConvert.SerializeObject(myDotNetObject, settings); 

I am currently using this solution to serialize an instance of IDictionary<string, object> , which may contain primitives.

Answer 2

Hacked it together and checked it. Obviously, this requires unit testing and is more a proof of concept. If you want a dirty solution to get started, this should begin.

https://github.com/xstos/Newtonsoft.Json/commit/8d3507cbba78f7096a82e42973e56d69c9541c42