Cosmos: Dictionary<int, string> properties do not generate any errors, but don't map correctly

[ajcvickers]

Code below works if the dictionary is Dictionary<string, string>.

public static class CosmosPrimitiveTypesSample
{
    public static void Collections_and_dictionaries_of_primitive_types()
    {
        Console.WriteLine($">>>> Sample: {nameof(Collections_and_dictionaries_of_primitive_types)}");
        Console.WriteLine();

        Helpers.RecreateCleanDatabase();

        #region Insert
        using var context = new BooksContext();

        var book = new Book
        {
            Title = "How It Works: Incredible History",
            Quotes = new List<string>
            {
                "Thomas (Tommy) Flowers was the British engineer behind the design of the Colossus computer.",
                "Invented originally for Guinness, plastic widgets are nitrogen-filled spheres.",
                "For 20 years after its introduction in 1979, the Walkman dominated the personal stereo market."
            },
            Notes = new Dictionary<int, string>
            {
                { 121, "Fridges" },
                { 144, "Peter Higgs" },
                { 48, "Saint Mark's Basilica" },
                { 36, "The Terracotta Army" }
            }
        };

        context.Add(book);
        context.SaveChanges();
        #endregion

        #region Updates
        book.Quotes.Add("Pressing the emergency button lowered the rods again.");
        book.Notes[48] = "Chiesa d'Oro";

        context.SaveChanges();
        #endregion

        Console.WriteLine();
    }

    public static class Helpers
    {
        public static void RecreateCleanDatabase()
        {
            using var context = new BooksContext(quiet: true);

            context.Database.EnsureDeleted();
            context.Database.EnsureCreated();
        }
    }

    #region BookEntity
    public class Book
    {
        public Guid Id { get; set; }
        public string Title { get; set; }
        public IList<string> Quotes { get; set; }
        public Dictionary<int, string> Notes { get; set; }
    }
    #endregion

    public class BooksContext : DbContext
    {
        public DbSet<Book> Books { get; set; }

        private readonly bool _quiet;

        public BooksContext(bool quiet = false)
        {
            _quiet = quiet;
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<Book>().ToContainer("books");
        }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder
                .EnableSensitiveDataLogging()
                .UseCosmos(
                "https://localhost:8081",
                "C2y6yDjf5/R+ob0N8A7Cgv30VRDJIWEHLM+4QDU5DE2nQ9nDuVTqobD4b8mGGyPMbIZnqyMsEcaGQy67XIw/Jw==",
                "EFCoreSample");

            if (!_quiet)
            {
                optionsBuilder.LogTo(
                    Console.WriteLine,
                    new[] { CosmosEventId.ExecutedCreateItem, CosmosEventId.ExecutingSqlQuery, CoreEventId.SaveChangesCompleted });
            }
        }
    }
}

Document:

{
    "Id": "b5940ee9-36ea-4986-87a6-76163a45f40a",
    "Discriminator": "Book",
    "Quotes": [
        "Thomas (Tommy) Flowers was the British engineer behind the design of the Colossus computer.",
        "Invented originally for Guinness, plastic widgets are nitrogen-filled spheres.",
        "For 20 years after its introduction in 1979, the Walkman dominated the personal stereo market.",
        "Pressing the emergency button lowered the rods again."
    ],
    "Title": "How It Works: Incredible History",
    "id": "Book|b5940ee9-36ea-4986-87a6-76163a45f40a",
    "Notes": {},
    "_rid": "ESsgAJPQFeoBAAAAAAAAAA==",
    "_self": "dbs/ESsgAA==/colls/ESsgAJPQFeo=/docs/ESsgAJPQFeoBAAAAAAAAAA==/",
    "_etag": "\"00000000-0000-0000-9b53-8a4362ae01d7\"",
    "_attachments": "attachments/",
    "_ts": 1630076113
}

[ajcvickers]

Note from triage: only string-keyed dictionaries are supported. This should throw in model validation or similar.