fatihyildizhan fatihyildizhan - 1 year ago 343
C# Question

MongoDB .Net driver 2.0 Pull (remove element)

Can you help me to run correctly "Pull (remove)" with 2.0 driver.

I have a collection like this and I want to remove first follower named as fethiye by follower field.

"_id": ObjectId("554e05dfc90d3d4dfcaa2aea"),
"username": "bodrum",
"followerList": [
"_id": ObjectId("554e0625a51586362c33c6df"),
"follower": "fethiye",
"avatar": "fethiye.png"
"_id": ObjectId("554e0625a51586362c33c6df"),
"follower": "izmir",
"avatar": "izmir.png"

How can I fix this query?

var filter = new BsonDocument("username", "bodrum");
var update = Builders<Person>.Update.Pull("followerList:follower", "fethiye");
Person pr = collection.FindOneAndUpdateAsync(filter, update).Result;


Answer Source

When using a filter to remove array elements, you need to use the PullFilter builder instead of Pull (which matches whole elements).

var collection = db.GetCollection<Person>("people");
var filter = new BsonDocument("username", "bodrum");
var update = Builders<Person>.Update.PullFilter("followerList",
    Builders<Follower>.Filter.Eq("follower", "fethiye"));
var result = collection.FindOneAndUpdateAsync(filter, update).Result;

Or somewhat more succinctly, using lambdas:

var update = Builders<Person>.Update.PullFilter(p => p.followerList,
                                                f => f.follower == "fethiye");
var result = collection
    .FindOneAndUpdateAsync(p => p.username == "bodrum", update).Result;
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