MongoDB .Net 驱动程序 2.0 拉（删除元素）

Question

你能帮我运行使用 2.0 驱动程序正确 "Pull (remove)" 吗？

我有一个这样的 collection，我想删除第一个被关注者字段命名为 fethiye 的关注者。

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

我该如何修正这个查询？

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

谢谢。

Answer 1

当使用过滤器删除数组元素时，您需要使用 PullFilter 生成器而不是 Pull（匹配整个元素）。

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;

或者更简洁一些，使用 lambda：

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

这是我用来删除嵌套数组对象的方法

-父路径：followerList
-属性：follower
-值：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);

删除更深嵌套数组对象的示例：
让我们删除名称为 Doe

的对象

-父路径：followerList.0.testArray
-属性：name
-值：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"
    }
  ]
}

Answer 3

我可以使用 MongoDB.Entities 提供一个更简单的解决方案吗？ person 和 followers 存储在它们自己的集合中，代表一对多关系。

using System.Linq;
using MongoDB.Entities;

namespace Whosebug
{
    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);
        }
    }
}

Answer 4

假设你有一个名为 Person 的集合，您可以使用 PullFilter 从 array

中删除记录

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}");

如果我们还需要删除已过滤文档中的值数组，我们可以用此行替换更新生成器

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

同样为了保存多个文档，updateOne可以替换成updateMany

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

MongoDB .Net 驱动程序 2.0 拉（删除元素）

MongoDB .Net driver 2.0 Pull (remove element)

c#

mongodb

mongodb-.net-driver