从BSON序列化为JSON

Question

I'm trying to serialize some BSON returned from MongoDB into JSON:

var bson = MongoDB.Bson.BsonDocument.Parse(@"{
    ""_id"": ObjectId(""5a45a64ec7fe121dfc673c6f""),
    ""MyOtherId"": ObjectId(""5a45a64dc7fe121dfc673c6e""),
    ""Blah"": ""Test""
}");

And I want to morph the ObjectID into a string so I get

"_id": "5a45a64ec7fe121dfc673c6f",

instead of

"_id": {"$oid": "5a4597a3d999f209e05df993"},

so I tried this:

var result = Newtonsoft.Json.JsonConvert.SerializeObject(bson, new Newtonsoft.Json.Bson.Converters.BsonDataObjectIdConverter());

But I get an error:

Newtonsoft.Json.JsonSerializationException: 'Error getting value from 'AsBoolean' on 'MongoDB.Bson.BsonObjectId'.'

Inner exception: InvalidCastException: Unable to cast object of type 'MongoDB.Bson.BsonObjectId' to type 'MongoDB.Bson.BsonBoolean'.

I still get the error with the simplified version:

var result = Newtonsoft.Json.JsonConvert.SerializeObject(bson);

using Newtonsoft.Json v10.0.3 and MongoDB.Driver v2.5.0

Answer 1

Newtonsoft tries to read every property of an object into a Json value. So if your object has public string Lol {get { throw new Exception}} , Newtonsoft will try to read Lol , get the exception, and will fail serializing.

Now, a Bson value has lots of properties like AsBoolean , AsString , which throw an exception if the actual value isn't what they expect. Mongo expects you to know what value is contained in the bson and access the appropriate proeprty. But since Newtonsoft tries to access all properties, you get that error.

You can work around that issue by writing a custom converter for BsonValue and passing it to Newtonsoft in the SerializationSettings. Your converter will need to call getBsonType() on the VsonValue, and then the correct AsBoolean , AsInt or whatever to get the actual value.