.NET 10 > Using `jsonb` for `ImmutableHashSet<string>` does not work anymore

[pimeggermont]

original class

public class Car
{
    public int Id { get; init; }
    
    [Column(TypeName = "jsonb")] public ImmutableHashSet<string> Windows { get; init; }
    [Column(TypeName = "jsonb")] public ImmutableHashSet<Wheel> Wheels { get; init; }
    [Column(TypeName = "jsonb")] public ImmutableList<Door> Doors { get; init; }
    [Column(TypeName = "jsonb")] public ImmutableList<string> Stickers { get; init; }
}

After updating our code base to .NET 10 we bumped into some build time errors in regards of the [Column(TypeName = "jsonb")] ImmutableHashset<string> Windows.

Error : The exception 'The type 'ImmutableHashSet<string>' cannot be used as a primitive collection because it is not an array and does not implement 'IList<string>'

We tried to change these ImmutableHashSet<string> to List<string>, after this changes we could run the app again. But when we inserted a row in the database with a [Column(TypeName = "jsonb")] ImmutableList<string> our application crashed.

Error: No parameterless constructor defined for type 'System.Collections.Immutable.ImmutableList1'[System.String]'.

After not using the attribute anymore as it is deprecated, we declared our columns as jsonb in the DbContext. These runs without any problems but the data saved in the database only saves the 'capacity' property of the List {"Capacity": 2}

I created a POC of how our code is setup with different branches for each problem we bumped into: (explanation of the branches in the readme)
https://github.com/pimeggermont/poc_dotnet10

An example of all the different data inserted in the database for each possible attempt

Is this intended or regression?

Looking forward to your reply!

[roji]

@pimeggermont there's really a lot going on in your multiple samples and bug reports, I'll try to outline the latest best practices.

First, since you're mapping a list of scalars (primitive collection), in PostgreSQL it's recommended to just map that to a PostgreSQL array. The EF provider will do that automatically for you:

Array mapping

await using var context = new BlogContext();
await context.Database.EnsureDeletedAsync();
await context.Database.EnsureCreatedAsync();

context.Blogs.Add(new Blog { Windows = new List<string> { "a", "b" } });
await context.SaveChangesAsync();

public class BlogContext : DbContext
{
    public DbSet<Blog> Blogs { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        => optionsBuilder
            .UseNpgsql("Host=localhost;Username=test;Password=test;Database=test")
            .LogTo(Console.WriteLine, LogLevel.Information)
            .EnableSensitiveDataLogging();
}

public class Blog
{
    public int Id { get; set; }
    public List<string> Windows { get; set; }
}

If you insist on mapping your scalar list to JSON instead of an array in the database (I'd love to hear why), you can indeed set the column type to jsonb on the list property (please use version 10 of the provider):

Working code mapping List<> to jsonb

await using var context = new BlogContext();
await context.Database.EnsureDeletedAsync();
await context.Database.EnsureCreatedAsync();

context.Blogs.Add(new Blog { Windows = new List<string> { "a", "b" } });
await context.SaveChangesAsync();

public class BlogContext : DbContext
{
    public DbSet<Blog> Blogs { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        => optionsBuilder
            .UseNpgsql("Host=localhost;Username=test;Password=test;Database=test")
            .LogTo(Console.WriteLine, LogLevel.Information)
            .EnableSensitiveDataLogging();
}

public class Blog
{
    public int Id { get; set; }
    [Column(TypeName = "jsonb")]
    public List<string> Windows { get; set; }
}

In your dotnet-10-v2 scenario I'm seeing various odd stuff: first, UseJsonNet() should not be used, that's the old .NET JSON serializer and EF will use the built-in System.Text.Json instead; JsonSerializerOptions is also not supported, since EF must be able to query your collection columns, and it's unaware of what you may have configured there. Finally, you're reporting an exception referring to ImmutableList, though we're only using List here.

If you're still encountering issues after all this, please try posting a minimal fragment just like the ones I posted above, which clearly shows what you're trying and how it's failing.