Document that subclasses Dictionary<string,bool> no longer Load'able on 4.2

[Josh Buedel]

We have a document class named FeatureFlag that inherits from Dictionary<string,bool>. On 4.2, we get exceptions when loading it. It worked fine on 3.5.  The attached unit test demonstrates the problem. Use the #define at the top to switch between 3.5 and 4.2.

The exception is "Newtonsoft.Json.JsonReaderException : Error reading boolean. Unexpected token: StartObject. Path '@metadata'."

[Egor Shamanaev]

Hello,
we are using the Json.Net library for serialization,
the library handles dictionaries without converting custom fields on class that inherits from dictionary. you can check that by var json = JsonConvert.SerializeObject(obj);
You can CustomizedJsonSerializer and register it in store conventions

For you example it should be something like this:

    public class FeatureFlagsConverter : JsonConverter

    {

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

        {

            if (value == null)

            {

                writer.WriteNull();

                return;

            }

            var val = (FeatureFlags)value;

            writer.WriteStartObject();

            writer.WritePropertyName(nameof(val.DocumentID));

            writer.WriteValue(val.DocumentID);

            foreach (var kvp in val)

            {

                writer.WritePropertyName(kvp.Key);

                writer.WriteValue(kvp.Value);

            }

            writer.WriteEndObject();

        }

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

        {

            // TODO

            return null;

        }

        public override bool CanConvert(Type objectType)

        {

            return objectType == typeof(FeatureFlags);

        }

    }

[Josh Buedel]

Thanks for the idea Egor. We ended up moving the dictionary to be a member variable, like below. Storing a dictionary directly isn't necessarily a use case we specifically need. It worked on 3.5 so this was more of a bug report than anything.

   public class FeatureFlags  

   {

      public Dictionary<string, bool> Flags = new Dictionary<string, bool>();