Mongo db C# add a new guid/objectid to document

Question

how to send a query like this from the C# driver to mongodb db.getCollection("myCollection").updateMany({}, {$set:{_uniqueId : "UUID()"}}) I have tried doing this :

                var pipeline = PipelineDefinition<BsonDocument, BsonDocument>.Create(new BsonDocument()
            {
                {"$addFields", new BsonDocument(){{"_uniqueId" , new BsonDocument()
                    {
                            {"$function" , new BsonDocument()
                            {
                                {"body" , "function(){ return new UUID()}"},
                                {"args" , new BsonArray()},
                                {"lang" , "js"},
                            }}
                    }
                }}}
            });

            var definition = Builders<BsonDocument>.Update.Pipeline(pipeline);
            mongoDatabase.GetCollection<BsonDocument>(set.CollectionName).UpdateMany(Builders<BsonDocument>.Filter.Empty, definition);

but i just get and empty _uniqueId

Answer 1

I have found something that works, I will be glad if someone found a simpler solution to this.

                var pipeline = PipelineDefinition<BsonDocument, BsonDocument>.Create(new BsonDocument()
            {
                {"$addFields", new BsonDocument(){{"_uniqueId" , new BsonDocument()
                    {
                        {"$toObjectId", new BsonDocument(){
                            {"$function" , new BsonDocument()
                            {
                                {"body" , "function(){var id = new ObjectId(); return id.valueOf()}"},
                                {"args" , new BsonArray()},
                                {"lang" , "js"},
                            }}
                        }}
                    }
                }}}
            });