RavenDB Simple join with multimap reduce

SimpleJoinWithMultimapReduce.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Raven.Client.Indexes;
using Raven.Client;
using Raven.Client.Embedded;
using Raven.Json.Linq;

namespace SimpleJoinWithMultimapReduce
{

    public class Product
    {
        public string Id { get; set; }
        public string Name { get; set; }
    }

    public class ProductStats
    {
        public string Id { get; set; } // Products/1/Stats
        public int ViewCount { get; set; }
    }

    public class ProductWithStats
    {
        public string ProductId { get; set; }
        public string Name { get; set; }
        public int? ViewCount { get; set; }

    }


    public class Products_WithStats : AbstractMultiMapIndexCreationTask<ProductWithStats>
    {
        public Products_WithStats()
        {

            AddMap<ProductStats>(stats => from s in stats
                                          select new
                                          {
                                              ProductId = s.Id.Replace("/Stats", string.Empty),
                                              Name = (string) null,
                                              ViewCount = (int?) s.ViewCount
                                          });

            AddMap<Product>( products => from p in products
                                         select new 
                                         {
                                             ProductId = p.Id,
                                             Name = p.Name,
                                             ViewCount = (int?) null 
                                         });



            Reduce = results => from result in results
                                group result by result.ProductId into g
                                select new 
                                {
                                    ProductId = g.Key,
                                    Name = g.Select(x => x.Name).FirstOrDefault(x => x != null),
                                    ViewCount = g.Select(x => x.ViewCount).FirstOrDefault(x => x != null)
                                };

            Index("Name", Raven.Abstractions.Indexing.FieldIndexing.Analyzed);     
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            using (var store = new EmbeddableDocumentStore { RunInMemory = true })
            {
                store.Initialize();
                new Products_WithStats().Execute(store);

                using (var session = store.OpenSession())
                {
                    session.Store ( new Product { Id = "Products/1", Name = "Gazpacho andaluz" } );
                    session.Store ( new ProductStats { Id = "Products/1/Stats", ViewCount = 2 } );
                    session.SaveChanges();

                    var query = session.Query<ProductWithStats, Products_WithStats>()                      
                        .Customize(x => x.WaitForNonStaleResults())
                        .Search(x => x.Name, "Gazp*", escapeQueryOptions: EscapeQueryOptions.AllowPostfixWildcard);

                    Console.WriteLine(query);

                    var productsWithStats = query.ToList();

                    var statistics = store.DatabaseCommands.GetStatistics();

                    foreach (var pws in productsWithStats)
                    {
                        Console.WriteLine ( RavenJObject.FromObject(pws).ToString());
                    }

                    Console.WriteLine("Press enter...");
                    Console.ReadLine();
                }
            }
        }
    }
}