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How to select attached documents in mongodb?

Suppose I have nested documents with this structure:

{
    "_id": "a125",
    "Language": null,
    "Name": "Some name",
    "Related": [{
        "_id": "b125",
        "Status": 0,
    }, {
        "_id": "b126",
        "Status": 1,
    }]
}

is it possible with C # drivers to select the "Linked" model where id is b126 and at the same time get the id of the parent document (a125)?

As I think the result should look like this:

{
  "_id": "a125",
  "Related": {
     "_id": "b126",
     "Status": 1,
  }
}
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2 answers


You can use dot notation with the positional$

projection operator to find the matching document and include only the matching element Related

.

In the shell:

db.test.findOne({'Related._id': 'b125'}, {'Related.$': 1})


To do this in C #:

var filter = Builders<BsonDocument>.Filter.Eq("Related._id", "b125");
var projection = Builders<BsonDocument>.Projection.Include("Related.$");
var result = await collection.Find(filter).Project(projection).FirstAsync();
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You should use dot notation for your purpose. Your request will look like this:

{"Related._id": "b126"}


This will bring you all documents with all fields, including the parent _id

, where there is a document element in the array Related

that has a field _id

with a value"b126"

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