Updating an embedded document (2 levels in depth) in MongoDB using the official C # driver

I am having problems updating an embedded document, which is at 2 levels in the document.

I read this post Updating the embedded document in MongoDB with the official C # driver , but this problem had only 1 level of depth and therefore the syntax needs are probably different.

What is the correct syntax for updating the next embedded document using the official 10th generation C # driver version 1.0?

{
  "_id": {
    "$oid": "4dfa2601dc1c791d40106a25"
  },
  "_t": "Model",
  "TypeId": 1,
  "Title": "Some Title",
  "ObjectBags": [
    {
      "_t": "ObjectBag",
      "_id": {
        "$oid": "4dfa2603dc1c791d40107e48"
      },
      "TypeId": 4,
      "Objects": [
        {
          "_t": "DomainObject",
          "_id": {
            "$oid": "4dfa2603dc1c791d40107e49"
          },
          "TypeId": 4,
          "ParentId": {
            "$oid": "4dfa2603dc1c791d40107e48"
          },
          "CreatedBy": "me",
          "CreatedDate": "Thu, 16 Jun 2011 08:49:21 GMT -07:00",
          "LastUpdatedBy": "me",
          "LastUpdatedDate": "Thu, 16 Jun 2011 08:49:21 GMT -07:00",
          "InactivatedDate": null,
          "Data": "1`|`11536"
        }
      ]
    }
  ]
}

This is what I tried, I get no errors, but nothing is updated.

var models = _database.GetCollection<Model>("Models");
var model = models.FindOneAs<Model>(Query.EQ("_id", new ObjectId("4dfa2601dc1c791d40106a25")));

var wspwRef = model.Objects.Find(Domain.Object.Reference);
wspwRef.Set(Domain.Field.Reference.Name, "SOME REF RM");

var query = Query.EQ("ObjectBags.Objects._id", new ObjectId("4dfa2603dc1c791d40107e49"));
var documentWrapper = BsonDocumentWrapper.Create<DomainObject>(wspwRef);
models.Update(query, Update.Set("ObjectBags.Objects.$", documentWrapper));

DocumentWrapper generates the next from a recently updated object

{ 
  "_id" : { "$oid" : "4dfa2603dc1c791d40107e49" }, 
  "TypeId" : 4, 
  "ParentId" : { "$oid" : "4dfa2603dc1c791d40107e48" }, 
  "CreatedBy" : "me", 
  "CreatedDate" : { "$date" : 1308239361784 }, 
  "LastUpdatedBy" : "me", 
  "LastUpdatedDate" : { "$date" : 1308239791540 }, 
  "InactivatedDate" : null, 
  "Data" : "1`|`11536^|^2`|`SOME NEW TEXT" 
}

, "ObjectBags.Objects. $" - .