MongoDB .Net 驱动程序 2.0 Pull(删除元素) [英] MongoDB .Net driver 2.0 Pull (remove element)

问题描述

你能帮我用 2.0 驱动程序正确运行Pull (remove)"吗.

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

我有一个这样的集合，我想删除第一个通过关注者字段命名为 fethiye 的关注者.

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"
    }
  ]
} 

如何解决此查询?

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

谢谢.

推荐答案

当使用过滤器移除数组元素时，需要使用PullFilter 构建器而不是 Pull(匹配整个元素).

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;

或者更简洁地说，使用 lambda:

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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