Jess.NET Deserialization into a dynamic object with binding

Question

How can I get Json.NET to deserialize in dynamic objects, but still make reference resolution?
dynamic d=JsonConvert.DeserializeObject<ExpandoObject>(...) exactly the same as
dynamic d=JsonConvert.DeserializeObject(...) returns a dynamic object, but does not allow parts of $ref and $id . (An ExpandoObject eo , for example, has only eo["$ref"]="..." and does not have the properties that it should have, since it does not match $id -Object)

What I found out is that I need the permission of the contract resolver for a dynamic contract - which ExpandoObject only works if I explicitly specify Json.NET with a custom ContractResolver .

It still seems that ExpandoObject parsed using its own converter, and it fails again.

I tried my own class, inheriting from IDynamicMetaObjectProvider , which led to an infinite loop and did not seem to be correct. I would actually expect some simple solution to get ExpandoObject have link resolution.

Any help?

Answer 1

The way I did it now is a post-processing step and a recursive function that executes its own repository with saving and rebuilding:

  private static void Reffing(this IDictionary<string, object> current, Action<object> exchange,IDictionary<string, object> refdic) { object value; if(current.TryGetValue("$ref", out value)) { if(!refdic.TryGetValue((string) value, out value)) throw new Exception("ref not found "); if (exchange != null) exchange(value); return; } if (current.TryGetValue("$id", out value)) { refdic[(string) value] = current; } foreach (var kvp in current.ToList()) { if (kvp.Key.StartsWith("$")) continue; var expandoObject = kvp.Value as ExpandoObject; if(expandoObject != null) Reffing(expandoObject,o => current[kvp.Key]=o,refdic); var list = kvp.Value as IList<object>; if (list == null) continue; for (var i = 0; i < list.Count; i++) { var lEO = list[i] as ExpandoObject; if(lEO!=null) Reffing(lEO,o => list[i]=o,refdic); } } } 

used as:

  var test = JsonConvert.DeserializeObject<ExpandoObject>(...); var dictionary = new Dictionary<string, object>(); Reffing(test,null,dictionary); 

Answer 2

Since Json.NET is open source and its MIT license allows you to modify , the easiest solution may be to adapt its ExpandoObjectConverter to suit your needs:

 /// <summary> /// Converts an ExpandoObject to and from JSON, handling object references. /// </summary> public class ObjectReferenceExpandoObjectConverter : JsonConverter { // Adapted from https://github.com/JamesNK/Newtonsoft.Json/blob/master/Src/Newtonsoft.Json/Converters/ExpandoObjectConverter.cs public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer) { // can write is set to false throw new NotImplementedException(); } public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer) { return ReadValue(serializer, reader); } private object ReadValue(JsonSerializer serializer, JsonReader reader) { while (reader.TokenType == JsonToken.Comment) { if (!reader.Read()) throw reader.CreateException("Unexpected end when reading ExpandoObject."); } switch (reader.TokenType) { case JsonToken.StartObject: return ReadObject(serializer, reader); case JsonToken.StartArray: return ReadList(serializer, reader); default: if (JsonTokenUtils.IsPrimitiveToken(reader.TokenType)) return reader.Value; throw reader.CreateException("Unexpected token when converting ExpandoObject"); } } private object ReadList(JsonSerializer serializer, JsonReader reader) { IList<object> list = new List<object>(); while (reader.Read()) { switch (reader.TokenType) { case JsonToken.Comment: break; default: object v = ReadValue(serializer, reader); list.Add(v); break; case JsonToken.EndArray: return list; } } throw reader.CreateException("Unexpected end when reading ExpandoObject."); } private object ReadObject(JsonSerializer serializer, JsonReader reader) { IDictionary<string, object> expandoObject = null; object referenceObject = null; while (reader.Read()) { switch (reader.TokenType) { case JsonToken.PropertyName: string propertyName = reader.Value.ToString(); if (!reader.Read()) throw new InvalidOperationException("Unexpected end when reading ExpandoObject."); object v = ReadValue(serializer, reader); if (propertyName == "$ref") { var id = (v == null ? null : Convert.ToString(v, CultureInfo.InvariantCulture)); referenceObject = serializer.ReferenceResolver.ResolveReference(serializer, id); } else if (propertyName == "$id") { var id = (v == null ? null : Convert.ToString(v, CultureInfo.InvariantCulture)); serializer.ReferenceResolver.AddReference(serializer, id, (expandoObject ?? (expandoObject = new ExpandoObject()))); } else { (expandoObject ?? (expandoObject = new ExpandoObject()))[propertyName] = v; } break; case JsonToken.Comment: break; case JsonToken.EndObject: if (referenceObject != null && expandoObject != null) throw reader.CreateException("ExpandoObject contained both $ref and real data"); return referenceObject ?? expandoObject; } } throw reader.CreateException("Unexpected end when reading ExpandoObject."); } public override bool CanConvert(Type objectType) { return (objectType == typeof(ExpandoObject)); } public override bool CanWrite { get { return false; } } } public static class JsonTokenUtils { // Adapted from https://github.com/JamesNK/Newtonsoft.Json/blob/master/Src/Newtonsoft.Json/Utilities/JsonTokenUtils.cs public static bool IsPrimitiveToken(this JsonToken token) { switch (token) { case JsonToken.Integer: case JsonToken.Float: case JsonToken.String: case JsonToken.Boolean: case JsonToken.Undefined: case JsonToken.Null: case JsonToken.Date: case JsonToken.Bytes: return true; default: return false; } } } public static class JsonReaderExtensions { public static JsonSerializationException CreateException(this JsonReader reader, string format, params object[] args) { // Adapted from https://github.com/JamesNK/Newtonsoft.Json/blob/master/Src/Newtonsoft.Json/JsonPosition.cs var lineInfo = reader as IJsonLineInfo; var path = (reader == null ? null : reader.Path); var message = string.Format(CultureInfo.InvariantCulture, format, args); if (!message.EndsWith(Environment.NewLine, StringComparison.Ordinal)) { message = message.Trim(); if (!message.EndsWith(".", StringComparison.Ordinal)) message += "."; message += " "; } message += string.Format(CultureInfo.InvariantCulture, "Path '{0}'", path); if (lineInfo != null && lineInfo.HasLineInfo()) message += string.Format(CultureInfo.InvariantCulture, ", line {0}, position {1}", lineInfo.LineNumber, lineInfo.LinePosition); message += "."; return new JsonSerializationException(message); } } 

And then use it like:

  var settings = new JsonSerializerSettings { PreserveReferencesHandling = PreserveReferencesHandling.Objects, ReferenceLoopHandling = ReferenceLoopHandling.Serialize }; settings.Converters.Add(new ObjectReferenceExpandoObjectConverter()); dynamic d = JsonConvert.DeserializeObject<ExpandoObject>(json, settings);