如何使用 Mongo/C# 从嵌套在另一个数组中的数组中删除一个项目

Question

I've found plenty of examples showing how to remove an item from an array within the root of a collection of documents and I can successfully add items to nested arrays. But I can't seem to make headway on removing or updating an item in a nested array.

An example would be where I have a collection of groups. In that group, there is an array(list) of Members. Each of those members could have multiple nicknames that they go by. I need to know how to go about deleting/updating a Nickname for a specific member.

Ex:

1. I wanted to update Member: Robert James' Nickname "Not Rick James" to "Rick"
2. Delete the Nickname "Smithy" from Member John Smith

// example mongo data
[{
 "_id": 482232389408781300,
 "Name": "Group A",
 "Members": [
  {
   "_id": "X4cLx72J9",
   "Name": "John Smith",
   "NickNames: [
     {
      "_id": "V2889Jw8",
      "Name": "Smithy"
     },
     {
      "_id": "V82lvi2",
      "Name": "Ol John"
     }
    ]
   },
   {
    "_id": "X4c7872J9",
   "Name": "Robert James",
   "NickNames: [
     {
      "_id": "V2Bl9Jw8",
      "Name": "Not Rick James"
     },
     {
      "_id": "V8Qrvi2",
      "Name": "Slick"
     }
    ]
   }
 }
]

// c# classes

class Group{
 public ulong Id {get;set;} // Unique Id
 public string Name {get;set;}
 public List<Member> Members{get;set;}
}

class Member{
 public string Id {get;set;} // Unique Id
 public string Name {get;set;}
 public List<NickName> NickNames{get;set;}
}

public NickName{
 public string Id {get;set;} // Unique Id
 public string Name {get;set;}
}

Editing for clarification I'm needing to know how to complete this request using the MongoDB driver for C#

var guilds = db.GetCollection<Group>("groups");
var filter = Builders<Group>.Filter;
/// At this point I'm unsure how the filter/update values should be coded in order to update the mongo db.

Answer 1

Assuming this is your data,

List<NickName> nickNameList = new List<NickName>();
nickNameList.Add(new NickName() { Id = "V2889Jw8", Name = "Smithy" });
nickNameList.Add(new NickName() { Id = "V82lvi2", Name = "Ol John" });

List<NickName> nickNameList2 = new List<NickName>();
nickNameList2.Add(new NickName() { Id = "V2Bl9Jw8", Name = "Not Rick James" });
nickNameList2.Add(new NickName() { Id = "V8Qrvi2", Name = "Slick" });

List<Member> members = new List<Member>();
members.Add(new Member() { Id = "X4cLx72J9", Name = "John Smith", NickNames = nickNameList });
members.Add(new Member() { Id = "X4c7872J9", Name = "Robert James", NickNames = nickNameList2 });

List<Group> group = new List<Group>();
group.Add(new Group(){
    Id = 482232389408781300,
    Name = "Group A",
    Members = members
});

We can use the .Find() method of List to find the specific record in the list and update or delete it.

For example:

//Update
group.Find(x => x.Id == 482232389408781300).Members.Find(x => x.Id == "X4c7872J9").NickNames.Find(n => n.Name == "Not Rick James").Name = "Rick";

//Delete
List<NickName> nickNames = group.Find(x => x.Id == 482232389408781300).Members.Find(x => x.Id == "X4cLx72J9").NickNames;
nickNames.Remove(nickNames.Find(n => n.Name == "Smithy"));

Answer 2

I think I've worked out two methods that work for me. They might not be the most efficient so I will continue reading more into. But here is what I have thus far.

The following deletion method uses the positional all '$[]' option as each Nickname has a unique ID.

// Delete An array item
var groupId = 482232389408781300;
var memberId = "X4cLx72J9";
var nickId = "V2889Jw8";

var collection = _db.GetCollection<Group>("groups");
var filter = Builders<Group>.Filter.Eq(group => group.Id, groupId);
var update = Builders<Group>.Update.PullFilter("Members.$[].NickNames", Builders<BsonDocument>.Filter.Eq("_id", nickId));
collection.UpdateOne(filter, update);

The update method is using the ArrayFilters option. I imagine you could use this for the deletion method as well.

// Update An array item
var groupId = 482232389408781300;
var memberId = "X4cLx72J9";
var nickId = "V2889Jw8";
var newNick = "Loon";

var collection = _db.GetCollection<Group>("groups");
var filter = Builders<Group>.Filter.Eq(group => group.Id, groupId);
var update = Builders<Group>.Update.Set("Members.$[m].NickNames.$[n].Name", newNick); 
var filterArray = new List<ArrayFilterDefinition>{
 new JsonArrayFilterDefinition<Group>(string.Format("{{'m._id': '{0}'}}", memberId)),
 new JsonArrayFilterDefinition<Group>(string.Format("{{'n._id': '{0}'}}", nickId))
};

var updateOptions = new UpdateOptions { ArrayFilters = filterArray };

collection.UpdateOne(filter, update, updateOptions);