The BsonDocument.ToJson() method returns invalid JSON since ObjectID() and ISODate not valid JSON.
BsonDocument.ToJson()
ObjectID()
ISODate
What is the best way to get valid JSON from a BSON arbitration document?
You can try something like this
var document = new BsonDocument("_id", ObjectId.GenerateNewId()); var jsonWriterSettings = new JsonWriterSettings { OutputMode = JsonOutputMode.Strict }; // key part Console.WriteLine(document.ToJson(jsonWriterSettings));
More information https://groups.google.com/forum/#!topic/mongodb-user/fQc9EvsPc4k