MongoDb C# Typed Aggregations with Group Unwind and Project

Question

I have a collection like this:

[{
  \"_id\": 1,
  \"OtherProperties\": 100
  \"PersonInventory\": [{
    \"FirstName\": \"Joe\",
    \"MiddleName\": \"Bob\",         


        

Answer 1

this can be easily achieved with the IMongoQueryable interface like shown below

using MongoDB.Entities;
using System.Linq;

namespace StackOverflow
{
    public class RootDoc : Entity
    {
        public Person[] PersonInventory { get; set; }
    }

    public class Person
    {
        public long PersonId { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
    }

    public class Program
    {
        private static void Main(string[] args)
        {
            new DB("test");

            (new[] {
                new RootDoc{
                    PersonInventory = new[]{
                        new Person{ PersonId = 1, FirstName = "first", LastName="person"},
                        new Person{PersonId = 2, FirstName = "second", LastName="person"}
                    }
                },
                new RootDoc{
                    PersonInventory = new[]{
                        new Person { PersonId = 2, FirstName = "second", LastName = "person" } }
                }
            }).Save();

            var uniquePersons = DB.Queryable<RootDoc>()
                                  .Where(r => r.PersonInventory.Any())
                                  .SelectMany(r => r.PersonInventory)
                                  .Distinct()
                                  .ToArray();
        }
    }
}

above code uses my library MongoDB.Entities for brevity. just replace DB.Queryable<RootDoc>() with collection.AsQueryable() for official driver.

Answer 2

I did some digging on the mongodb Jira pages, it looks like there isn't support for the variable $$ROOT, so the above queries are not supported.