Update/Delete a sub document in mongodb using C# driver

Question

I have 2 classes:

public class Vote
{
    public string VoteId { get; set; }
    public string Question { get; set; }
    public List Answe         


        

Answer 1

// Example function for update like count add like user  using c#    
public PostModel LikeComment(LikeModel like)
{
    PostModel post = new PostModel();

    _client = new MongoClient();
    _database = _client.GetDatabase("post");
    var collection = _database.GetCollection<PostModel>("post");

    var _filter = Builders<PostModel>.Filter.And(
    Builders<PostModel>.Filter.Where(x => x.PostId == like.PostId),
    Builders<PostModel>.Filter.Eq("Comments.CommentId", like.CommentId));

    var _currentLike = collection.Find(Builders<PostModel>.Filter.Eq("PostId", like.PostId)).FirstOrDefault().Comments.Find(f => f.CommentId == like.CommentId).Like;

    var update = Builders<PostModel>.Update.Set("Comments.$.Like", _currentLike + 1);
    collection.FindOneAndUpdate(_filter, update);

    var addUser = Builders<PostModel>.Update.Push("Comments.$.LikeUsers", like.UserId);
    collection.FindOneAndUpdate(_filter, addUser);

    var _findResult = collection.Find(_filter).FirstOrDefault();

    return _findResult;
}

Answer 2

//Delete comment
public PostModel delcomment(int postId, int commentId)
{
    _client = new MongoClient();
    _database = _client.GetDatabase("post");
    var collection = _database.GetCollection<PostModel>("post");

    var filter = Builders<PostModel>.Filter.Eq("PostId", postId);

    var update = Builders<PostModel>.Update.PullFilter("Comments",
    Builders<Comments>.Filter.Eq("CommentId", commentId));

    collection.FindOneAndUpdate(filter, update);

    var _findResult = collection.Find(filter).FirstOrDefault();
    return _findResult;
}

Answer 3

To update subdocument you can use this:

var update = Update.Set("AnswerList.$.OptionName", "new").Set("AnswerList.$.VoteCount", 5);
collection.Update(Query.And(Query.EQ("_id", new BsonObjectId("50f3c313f216ff18c01d1eb0")), Query.EQ("AnswerList.OptionId", "1")), update);

profiler:

"query" : { "_id" : ObjectId("50f3c313f216ff18c01d1eb0"), "AnswerList.OptionId" : "1" },
"updateobj" : { "$set" : { "AnswerList.$.OptionName" : "new", "AnswerList.$.VoteCount" : 5 } }

And to remove:

var pull = Update<Vote>.Pull(x => x.AnswerList, builder => builder.EQ(q => q.OptionId, "2"));
collection.Update(Query.And(Query.EQ("_id", new BsonObjectId("50f3c313f216ff18c01d1eb0")), Query.EQ("AnswerList.OptionId", "2")), pull);

profiler:

"query" : { "_id" : ObjectId("50f3c313f216ff18c01d1eb0"), "AnswerList.OptionId" : "2" },
"updateobj" : { "$pull" : { "AnswerList" : { "OptionId" : "2" } } }

Another way is to update parent document with modified child collection.