MongoDB .Net driver 2.0 Pull (remove element)

Question

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;

Thanks.

Answer 1

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;

Answer 2

Assuming you have a collection name Person, You can use PullFilter to remove the records from array

var filterBuilder = Builders<Person>.Filter.Eq(person => person.username, "bodrum");

var updateBuilder = Builders<Person>.Update.PullFilter(p => p.followerList,
                       Builders<Person>.Filter.Eq(per => per.follower, "fethiye"));

var updateResult = collection.UpdateOne(filterBuilder, updateBuilder);

Console.WriteLine(
            $"MatchedCount: {updateResult.MatchedCount}, ModifiedCount: {updateResult.ModifiedCount}");

If we also need to remove array of values inside a filtered document we can replace the update builder with this line

var updateBuilder = Builders<Person>.Update.PullFilter(p => p.followerList,
                   Builders<Person>.Filter.In(per => per.follower, new List<string> {"fethiye", "izmir"}));

Also to save many document, updateOne can be replace with updateMany

var updateResult = collection.UpdateMany(filterBuilder, updateBuilder);

Answer 3

This is what i use to delete a nested array object

-parentpath: followerList
-propertie: follower
-value: fethiye.png

var filter = new BsonDocument("_id", ObjectId.Parse(id));

    var updateValues = Builders<object>.Update.PullFilter(parentPath,
        Builders<object>.Filter.Eq(propertie, value));
        DatabaseCollection.FindOneAndUpdate(filter, updateValues);

Example to delete a deeper nested array object:
Let's delete the object with the name Doe

-parentPath: followerList.0.testArray
-propertie:name
-value:Doe

    {
  "_id": ObjectId("554e05dfc90d3d4dfcaa2aea"),
  "username": "bodrum",
  "followerList": [
    {
      "_id": ObjectId("554e0625a51586362c33c6df"),
      "follower": "fethiye",
      "testArray": [
{
"name":"John"
},
{
"name":"Doe"
},
{
"name":"Jason"
}
]
    },
    {
      "_id": ObjectId("554e0625a51586362c33c6df"),
      "follower": "izmir",
      "avatar": "izmir.png"
    }
  ]
}