使用MongoDB C＃驱动程序2.2对嵌套字段进行强类型查询

Question

Consider the following structures

public class Parent
{
    public ObjectId Id { get; set; }    
    public IEnumerable<Child> Children { get; set; }
}

public class Child
{
    public string Value { get; set; }
}

I want to find all parents object whose children values are a superset of an array ie

var parents = new List<Parent>();
var values = new[] { "A", "B", "C" };
parents.Where(x => !values.Except(x.Children.Select(y => y.Value)).Any());

or

{ "Children.Value": { $all: ["A", "B", "C"] } }

I'd like to do it in a typed manner but the predicate translator doesn't support Enumerable.Select so this won't work:

Builders<Parent>.Filter.All(x => x.Children.Select(y => y.Value), values);

I'm currently using this workaround:

var filters = values.Select(x => Builders<Parent>.Filter.Where(y => y.Children.Any(z => z.Value == x)));
Builders<Parent>.Filter.And(filters);

Is there a better way without using a magic field name string?

Answer 1

IMongoClient _client = new MongoClient(@"mongodb://...");
IMongoDatabase _database = _client.GetDatabase("...");
IMongoCollection<Parent> _collection = _database.GetCollection<Parent>("q35135879");
var ca = new Child { Value = "A" };
var cb = new Child { Value = "B" };
var cc = new Child { Value = "C" };
var fdb = Builders<Parent>.Filter;
var filterLinq = fdb.All (x=>x.Children, new[] {ca, cb, cc});
var filterFieldDefinition = fdb.All("Children", new[] { ca, cb, cc });
var found1 = _collection.Find(filterLinq).ToList();
var found2 = _collection.Find(filterFieldDefinition ).ToList();
CollectionAssert.AreEqual(found1, found2);