Querying a subfield in documentdb

Question

For example I have a document below for collection = delivery:

{
    \"doc\": [
        {
            \"docid\": \"15\",
            \"deliverynum\": \"123\"         


        

Answer 1

In Mongo shell you can use the $(projection) operator:

db.collection.find({ "doc.deliverynum": "999" }, { "doc.$": 1 })

Corresponding C# code can look like below:

var q = Builders<Model>.Filter.ElemMatch(x => x.doc, d => d.deliverynum == "999");
var p = Builders<Model>.Projection.ElemMatch(x => x.doc, d => d.deliverynum == "999");

var data = Col.Find(q).Project(p).ToList();

You can also use q = Builders<Model>.Filter.Empty if you want to get all documents even if the don't contain deliverynum =``999