MongoDB: query date by year C#

Question

Having such a document:

var document = new BsonDocument
{
    { "address" , new BsonDocument
        {
            { "street", "2 Avenue" },
            { "zipcode", "10075" },
            { "building", "1480" },
            { "coord", new BsonArray { 73.9557413, 40.7720266 } }
        }
    },
    { "borough", "Manhattan" },
    { "cuisine", "Italian" },
    { "grades", new BsonArray
        {
            new BsonDocument
            {
                { "date", new DateTime(2014, 10, 1, 0, 0, 0, DateTimeKind.Utc) },
                { "grade", "A" },
                { "score", 11 }
            },
            new BsonDocument
            {
                { "date", new DateTime(2014, 1, 6, 0, 0, 0, DateTimeKind.Utc) },
                { "grade", "B" },
                { "score", 17 }
            }
        }
    },
    { "name", "Vella" },
    { "restaurant_id", "41704620" }
};

How would I query for grades.date.year = 2016?

Was trying:

var filter = Builders<BsonDocument>.Filter.Eq("grades.date.year", 2016);
var result = await collection.Find(filter).ToListAsync();

But I guess dot notation only works on the json doc, not the objects? Scoured the internet, but couldn't find a clean example.

EDIT: C# classes?

class Address
{
    public string street { get; set; }
    public string zipcode { get; set; }
    public string building { get; set; }
    public IEnumerable<double> coord { get; set; }
}

class Grade
{
    public DateTime date { get; set; }
    public string grade { get; set; }
    public int score { get; set; }
}

class TestX
{
    public ObjectId _id { get; set; }
    public Address address { get; set; }
    public string borough { get; set; }
    public string cuisine { get; set; }
    public IEnumerable<Grade> grades { get; set; }
    public string name { get; set; }
    public string restaurant_id { get; set; }
}

Answer 1

This requires aggregation framework. If you could post c# class then will update my answer to strongly typed c# , but now decided to project year inside project phase.

    public static void Main()
    {
        var client = new MongoClient("mongodb://localhost:27017");
        var database = client.GetDatabase("test");

        var collection = database.GetCollection<BsonDocument>("hammer");

        var project =
            BsonDocument.Parse(
                "{_id: 1,address: 1,borough: 1,cuisine: 1,grades: 1,name: 1,restaurant_id: 1,year: {$year: '$grades.date'}}");

        var aggregationDocument =
            collection.Aggregate()
                .Unwind("grades")
                .Project(project)
                .Match(BsonDocument.Parse("{'year' : {$in : [2013, 2015]}}"))
                .ToList();

        foreach (var result in aggregationDocument)
        {
            Console.WriteLine(result.ToString());
        }

        Console.ReadLine();
    }

edit

var aggregationDocument =
                collection.Aggregate<TestX>()
                    .Unwind<TestX>(x=>x.grades)
                    .Match(BsonDocument.Parse(
   "{$and:[{'grades.date':{$gte: ISODate('2012-01-01')}},{'grades.date':{$lt: ISODate('2013-01-01')}}]}"))
                    .ToList();

Answer 2

Couldn't another approach be to check if date is within that year.

I.e for 2016 using $gte: 2016-01-01 00:00:00 and $lt: 2017-01-01 00:00:00

Find objects between two dates MongoDB

There are probably functions for them in c# like Gte and Lt. There are probably some easy way to combine the filters like with an & or similar.