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.

JohnnyHK · Accepted Answer · 2016-08-22 14:48:27Z

64

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;

edited Aug 22, 2016 at 14:48

answered May 9, 2015 at 22:21

JohnnyHK

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2 Comments

Tolga Evcimen Over a year ago

What if the the document we want to pull was one level deeper? as in this question stackoverflow.com/questions/32995762/…

user734028 Over a year ago

what is "collection" variable here, can you show me the code for that? Thanks.

deeps · Accepted Answer · 2019-07-11 07:31:39Z

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);

windrider63 · Accepted Answer · 2018-03-22 13:53:50Z

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"
    }
  ]
}

Dĵ ΝιΓΞΗΛψΚ · Accepted Answer · 2019-05-06 16:12:02Z

may i offer a much simpler solution using MongoDB.Entities. the person and followers are stored in their own collections and represents a one-to-many relationship.

using System.Linq;
using MongoDB.Entities;

namespace StackOverflow
{
    public class Person : Entity
    {
        public string Username { get; set; }
        public Many<Follower> FollowerList { get; set; }

        public Person() => this.InitOneToMany(() => FollowerList);
    }

    public class Follower : Entity
    {
        public string Name { get; set; }
        public string Avatar { get; set; }
    }

    class Program
    {
        static void Main(string[] args)
        {
            new DB("followers");

            var person1 = new Person { Username = "bodrum"};
            person1.Save();

            var follower1 = new Follower { Name = "fethiye", Avatar= "fethiye.png" };
            follower1.Save();

            var follower2 = new Follower { Name = "izmir", Avatar = "izmir.png" };
            follower2.Save();

            person1.FollowerList.Add(follower1);
            person1.FollowerList.Add(follower2);

            var fathiye = person1.FollowerList.Collection()
                                              .Where(p => p.Name == "fethiye")
                                              .FirstOrDefault();

            person1.FollowerList.Remove(fathiye);
        }
    }
}

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