JSON.Net serializer ignoring JsonProperty?

Question

I have the following entity class:

public class FacebookComment : BaseEntity
{
    [BsonId(IdGenerator = typeof(ObjectIdGenerator))]
    [BsonRepresentation(MongoDB.Bson.BsonType.ObjectId)]
    [JsonProperty("_id")]
    public ObjectId Id { get; set; }

    public int? OriginalId { get; set; }
    public DateTime Date { get; set; }
    public string Message { get; set; }
    public string Sentiment { get; set; }
    public string Author { get; set; }
}

When this object is serialized to JSON, I want the Id field to be written as "_id":{...}. AFAIK, I should just have to pass the desired propertyname to the JsonProperty attribute; and I should be good to go. However, when I call JsonConvert.SerializeObject; it seems to ignore my attribute and renders this instead:

{
    Author: "Author name",
    Date: "/Date(1321419600000-0500)/",
    DateCreated: "/Date(1323294923176-0500)/",
    Id: {
        CreationTime: "/Date(0)/",
        Increment: 0,
        Machine: 0,
        Pid: 0,
        Timestamp: 0
    },
    Message: "i like stuff",
    OriginalId: null,
    Sentiment: "Positive"
}

As you can see, the Id field is being rendered with the wrong field name.

Any ideas? Been working on this issue for an hour; can't figure out why the serializer is seemingly ignoring my JsonProperty.

Any constructive input is greatly appreciated.

Answer 1

Short Answer: Make sure all your assemblies are referencing the SAME EXACT JSON.NET DLL. What's probably happening is you are applying [JsonProperty] from one DLL in one assembly, and serializing the object from a different assembly which is looking for a different [JsonProperty] and because the CLR object types are different it is effectively being ignored.

---

Longer Answer: I just had this problem but fortunately because I had one class that was working with JsonProperty and one that wasn't I was able to do some detective work.

I stripped the non-working class down to the bare minimum and compared it to the working class and couldn't see ANY differences - except for the fact that the non-working class was in a different assembly.

When I moved the class to the other assembly it worked perfectly as it should.

I poked around for a bit trying to look into JSON serialization of namespaces, but that didn't seem to apply so I looked at the references and sure enough I was referencing an old JSONNET3.5 DLL in my entities DLL and the NUGET 4.5 version in my main project file.

This gives me two instances of [JsonProperty] attribute (which is just a regular class) and just because they're named the same doesn't mean the serializer is going to even recognise the attribute.

Answer 2

This post helped me.

I used serialiser:

new JavaScriptSerializer().Serialize(message)

But rigtly use this:

JsonConvert.SerializeObject(message);

Answer 3

I fixed this issue by marking my Id property with [System.Runtime.Serialization.DataMember(Name="_id")] instead of JsonProperty. Still not entirely clear as to why it didn't work originally though...