I’m upgrading Npgsql from 7.0.11 to 8.0.2/8.0.3. There are a couple of types in PostgreSQL declared like this:

CREATE TYPE my_type AS ENUM (...)

In SQL, we try to insert or read these types like this:

SELECT foo::my_type FROM BAR
SELECT foo FROM BAR
INSERT INTO BAR(foo) VALUES(@Foo::my_type)

First, I started encountering errors like this:

Writing values of 'MyType[]' is not supported for parameters having no NpgsqlDbType or DataTypeName

Then I tried to mitigate it using the following code:

NpgsqlConnection.GlobalTypeMapper.MapEnum<MyType>("public.my_type", new CustomEnumTranslator());

And it seems that writing errors disappeared. However, the reading errors came up:

System.Data.DataException : Error parsing column 5 (foo=MyType[] - Object)
---- System.InvalidCastException : Unable to cast object of type 'MyType[]' to type 'System.String[]'.

Interestingly, the place where the exception occurs, works with the object value method parameter. At runtime it has a value of MyType[2] (array of 2 Enum values) and then it somehow tries to cast into string[].

Any ideas how to solve this?