Can't create list of enum type column

[artfulsage]

Hi. I have a problem with list of enum type column.

public enum Labels : short
{
  Label1 = 1,
  Label2 = 2,
  Label3 = 3,
}

public class Item
{
  public int Id { get; set; }
  public List<Labels> Labels { get; set; }
}

In migration:

 migrationBuilder.CreateTable(
  name: "Item",
  columns: table => new
  {
    Id = table.Column<int>(nullable: false),
    Labels = table.Column<List<Labels>>(nullable: true)
  },
  constraints: table =>
  {
    table.PrimaryKey("PK_Item", x => x.Id);
  });

In database after applying migration there is a table:

CREATE TABLE public."Item" (
    "Id" integer NOT NULL,
    "Labels" smallint[]
);

If I map Enum as said here https://www.npgsql.org/efcore/mapping/enum.html I have this error on saving data

42804: column "Labels" has type smallint[], and expression - labels[] (translation)

And if I don't map Enum I have this error on saving data

The CLR array type System.Collections.Generic.List`1[Labels] isn't supported by Npgsql or your PostgreSQL. If you wish to map it to an PostgreSQL composite type array you need to register it before usage, please refer to the documentation.

So please tell me is there a bug in library or in its usage.

[roji]

It seems like you forgot to map the enum as specified in the docs, place the following at the very start of your app:

NpgsqlConnection.GlobalTypeMapper.MapEnum<Labels>();

I've done a quick test with the following code and it seems like everything works well:

public enum Label : short
{
    Label1 = 1,
    Label2 = 2,
    Label3 = 3
}

public class Blog
{
    public int Id { get; set; }
    public string Name { get; set; }
    public Label Label { get; set; }
    public List<Label> Labels { get; set; }
    public Label[] LabelsArray { get; set; }
}

public class BlogContext : DbContext
{
    public const string ConnectionString = "Host=localhost;Database=test;Username=npgsql_tests;Password=npgsql_tests";

    public DbSet<Blog> Blogs { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder builder)
    {
        NpgsqlConnection.GlobalTypeMapper.MapEnum<Label>();
        builder.UseNpgsql(ConnectionString);
    }

    protected override void OnModelCreating(ModelBuilder builder)
    {
        builder.ForNpgsqlHasEnum<Label>();
    }
}

static void Main(string[] args)
{
    using (var ctx = new BlogContext())
    {
        ctx.Database.EnsureDeleted();
        ctx.Database.EnsureCreated();

        ctx.Add(new Blog {
            Name="WAT",
            Label=Label.Label2,
            Labels=new List<Label> { Label.Label2, Label.Label3 },
            LabelsArray = new Label[] { Label.Label2, Label.Label3 }
        });
        ctx.SaveChanges();
    }
}

[artfulsage]

I followed an example and added NpgsqlConnection.GlobalTypeMapper.MapEnum<Labels>(); to my code but just not pasted it here.

And truly your sample code works fine. But in my real project (not from issue) it seems that enum mapping does not work and column in table has type smallint[] instead of my_enum[]. I don't understand why this is happening. Anyway it seems that either there is no bug or my bug report isn't sufficient. So you may close this issue.

By the way did you plan to add an alternative way of enum mapping to their numeric values? Then there would not be any problems with enum renaming and expansion.

[roji]

And truly your sample code works fine. But in my real project (not from issue) it seems that enum mapping does not work and column in table has type smallint[] instead of my_enum[]. I don't understand why this is happening. Anyway it seems that either there is no bug or my bug report isn't sufficient. So you may close this issue.

OK, thanks... It could be that you're mapping the enum too late - this must be done before any EF-related things happen. In any case I'll close this for now, but if you understand what's going on and think there may be an issue, please post back here and I'll reopen.

By the way did you plan to add an alternative way of enum mapping to their numeric values? Then there would not be any problems with enum renaming and expansion.

Mapping enums as numeric values is actually the default behavior (since PostgreSQL is the only database I know of which actually has native enums). If you want that behavior, you should simply remove all enum mapping (both the ADO-level MapEnum() and the EF-level ForNpgsqlHasEnum()). However, I don't we've tested this extensively with non-default enums (i.e. short). If you encounter an issue there please open another issue.

[Gregory-Ledray]

I encountered a very similar problem with my own model. I had thought I had followed all of the instructions here: https://www.npgsql.org/doc/types/enums_and_composites.html?tabs=datasource

But when reviewing the generated Up migration protected override void Up(MigrationBuilder migrationBuilder), I found that although the enum was being created:

Npgsql:Enum:test_enum

The migration builder's AddColumn was for a list of ints instead of for a list of the enum.

Reviewing my implementation, I saw I had done MapEnum in Startup.cs as dataSourceBuilder.MapEnum<TestEnum>(); and then done a services.AddDbContext with the data source correctly. However I had NOT done so in OnConfiguring inside MyDBContext.cs. After I copy-pasted my dataSourceBuilder, dataSource, UseNpgsql, etc code over into OnConfiguring from Startup.cs and set up a new migration, I finally saw the correct column setup in my Up migration:

migrationBuilder.AddColumn<List<TestStaticClass.TestEnum>>(
                name: "Tests",
                table: "Tests",
                type: "test_enum[]",
                nullable: false);

So at least for me, I encountered a problem and found this Github solution because I was only doing MapEnum in Startup.cs and I did not do it in OnConfiguring in MyDBContext.cs

Names of classes have been changed in my examples so if you see something a bit off in the code-quotes that's why.