Include with Join stopped working on preview9

[solvingproblemswithtechnology]

Having a query like this:

dbset
    .Include(a => a.NavigationProperty)
    .Join(dbset1, left => left.Id, right => right.Id,
        (left, right) => new { Left = left, Right = right })
    .ToList();

The Property "NavigationProperty" is null. This is working on preview8.

Steps to reproduce

Having three entities with a NavigationProperty. Join a query with Includes.

Further technical details

EF Core version: 3.0.0-preview9.19423.6
Database Provider: Microsoft.EntityFrameworkCore.SqlServer
Operating system: Windows 10
IDE: Visual Studio 2019 16.3.0 preview 3.0

[smitpatel]

I am not able to reproduce this.
Here is the repro code

using System;
using System.Linq;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;

namespace EFSampleApp
{
    public class Program
    {
        public static void Main(string[] args)
        {
            using (var db = new MyContext())
            {
                // Recreate database
                db.Database.EnsureDeleted();
                db.Database.EnsureCreated();

                // Seed database
                db.Add(new Blog
                {
                    BlogDetails = new BlogDetails { Value = "BlogDetails" },
                    Title = "FirstBlog"
                });

                db.Add(new Author { Name = "First" });

                db.SaveChanges();
            }

            using (var db = new MyContext())
            {
                // Run queries
                var query = db.Blogs.Include(b => b.BlogDetails)
                    .Join(db.Authors, l => l.Id, r => r.Id, (l, r) => new { l, r })
                    .ToList();

                Console.WriteLine(query[0].l.Title);
                Console.WriteLine(query[0].l.BlogDetails.Value);
                Console.WriteLine(query[0].r.Name);
            }

            Console.WriteLine("Program finished.");
        }
    }


    public class MyContext : DbContext
    {
        private static ILoggerFactory ContextLoggerFactory
            => LoggerFactory.Create(b =>
            {
                b
                .AddConsole()
                .AddFilter("", LogLevel.Debug);
            });

        // Declare DBSets
        public DbSet<Blog> Blogs { get; set; }
        public DbSet<Author> Authors { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            // Select 1 provider
            optionsBuilder
                .UseSqlServer(@"Server=(localdb)\mssqllocaldb;Database=_ModelApp;Trusted_Connection=True;Connect Timeout=5;ConnectRetryCount=0")
                //.UseSqlite("filename=_modelApp.db")
                //.UseInMemoryDatabase(databaseName: "_modelApp")
                //.UseCosmos("https://localhost:8081", @"C2y6yDjf5/R+ob0N8A7Cgv30VRDJIWEHLM+4QDU5DE2nQ9nDuVTqobD4b8mGGyPMbIZnqyMsEcaGQy67XIw/Jw==", "_ModelApp")
                //.EnableSensitiveDataLogging()
                //.UseLoggerFactory(ContextLoggerFactory)
                ;
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            // Configure model
        }
    }

    public class Blog
    {
        public int Id { get; set; }
        public string Title { get; set; }
        public BlogDetails BlogDetails { get; set; }
    }

    public class BlogDetails
    {
        public int Id { get; set; }
        public string Value { get; set; }
    }

    public class Author
    {
        public int Id { get; set; }
        public string Name { get; set; }
    }
}

Output

FirstBlog
BlogDetails
First
Program finished.

Please post a runnable project (or modify above repro code) to demonstrate the issue you are seeing.

[DanoThom]

NOTE: I'm using the cosmosDb provider.

I can confirm this too in both dotnet and aspnetcore using the above code using the latest version 3.0.0-preview9.19423.6.

Additionally, Preview9 seems to now require explicit values or a model value generator for the int Id's in each model object or it fails.

[smitpatel]

CosmosDb does not support join on server side. Hence EF Core cannot translate it to server.

[divega]

@AndriySvyryd to find the duplicate.

[smitpatel]

Duplicate of #16920