Implementation of BsonDocumentBackedClass serializer, with id generation and concrete property

MongoDocumentClassSerializer.cs

using System;
 
using MongoDB.Bson;
using MongoDB.Bson.Serialization;
using MongoDB.Bson.Serialization.IdGenerators;
using MongoDB.Bson.Serialization.Serializers;
 
public class MongoDocumentClassSerializer : BsonDocumentBackedClassSerializer<MongoDocument>, IBsonIdProvider
{
    public MongoDocumentClassSerializer()
    {
        this.RegisterMember("Id", "_id", ObjectIdSerializer.Instance, typeof(ObjectId), null);
    }
 
    protected override MongoDocument CreateInstance(BsonDocument backingDocument)
    {
        return new MongoDocument(backingDocument, this);
    }
 
    public bool GetDocumentId(object document, out object id, out Type idNominalType, out IIdGenerator idGenerator)
    {
        idNominalType = typeof(ObjectId);
        idGenerator = ObjectIdGenerator.Instance;
 
        var mongoDocument = document as MongoDocument;
        if (mongoDocument == null)
        {
            id = null;
            return false;
        }
 
        id = mongoDocument.Id;
        return true;
    }
 
    public void SetDocumentId(object document, object id)
    {
        var mongoDocument = document as MongoDocument;
        if (mongoDocument != null)
        {
            mongoDocument.Id = (ObjectId)id;
        }
    }
}