MongoDB的净驱动2.0拉（删除元素） [英] MongoDB .Net driver 2.0 Pull (remove element)

问题描述

您可以帮我正确运行拉（删除）以2.0驱动程序。

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

我有这样的一个集合，我想删除由跟随场命名为费特希耶第一个追随者。

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"
    }
  ]
} 

我怎样才能解决这个查询？

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;

感谢。

推荐答案

在使用过滤器除去数组元素，你需要使用 PullFilter 建设者，而不是拉（它匹配所有元素）。

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;

或有点更简洁，使用lambda表达式：

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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