model.cs

    public class GameContext : DbContext
    {
        public DbSet<Unit> Units { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder
                .UseNpgsql("Host=192.168.1.27;Database=tac_scribe;Username=tac_scribe;Password=tac_scribe",
                    o => o.UseNetTopologySuite())
            .UseSnakeCaseNamingConvention();
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<Unit>()
                .Property(b => b.Id).HasColumnName("id");
        }
    }

    public class Unit
    {
        [Column("id")]
        public string Id { get; set; }
        [Column(TypeName="geography (point)")]
        public Point Position { get; set; }
        public double Altitude { get; set; }
        public string Type { get; set; }
        public string Name { get; set; }
        public string Pilot { get; set; }
        public string Group { get; set; }
        public int Coalition { get; set; }
        public int Heading { get; set; }
        public DateTime UpdatedAt { get; set; }
        public int Speed { get; set; }
        public bool Deleted { get; set; }

        public List<Unit> Units { get; } = new List<Unit>();
    }

table.sql

-- Table: public.units

-- DROP TABLE public.units;

CREATE TABLE public.units
(
    id text COLLATE pg_catalog."default" NOT NULL,
    "position" geography NOT NULL,
    altitude double precision NOT NULL DEFAULT 0,
    type text COLLATE pg_catalog."default",
    name text COLLATE pg_catalog."default",
    pilot text COLLATE pg_catalog."default",
    "group" text COLLATE pg_catalog."default",
    coalition integer NOT NULL,
    heading integer,
    updated_at timestamp without time zone NOT NULL,
    deleted boolean,
    speed integer NOT NULL,
    CONSTRAINT units_pkey PRIMARY KEY (id)
)
WITH (
    OIDS = FALSE
)
TABLESPACE pg_default;

ALTER TABLE public.units
    OWNER to tac_scribe;

Table "units" is existing table and has string "id" field as primary key.

EFCore is throwing an exception because it is looking for u.UnitId / u.unit_id (if using the UseSnakeCaseNamingConvention) column despite the Column annotation and the fluent HasColumnName API call.

Enabled logging. The above code along with the following select

await using (var db = new GameContext())
{
  var unit = db.Units
  .First();
}

Results in the following SQL which includes a spurious u.unit_id. Looks like some sort of bug with primary key naming

2020-11-27 01:38:12.6703 DEBUG | Main | RurouniJones.DCS.OverlordBot.Overlord.Npgsql | Executing statement(s):
        SELECT u.id, u.altitude, u.coalition, u.deleted, u."group", u.heading, u.name, u.pilot, u.position, u.speed, u.type, u.unit_id, u.updated_at
FROM units AS u
LIMIT 1

This is happening even if we remove all the customisation and have

    public class GameContext : DbContext
    {
        public DbSet<Unit> Units { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder
                .UseNpgsql("Host=192.168.1.27;Database=tac_scribe;Username=tac_scribe;Password=tac_scribe",
                    o => o.UseNetTopologySuite())
            .UseSnakeCaseNamingConvention();
        }
    }

    public class Unit
    {
        public string Id { get; set; }
        [Column(TypeName="geography (point)")]
        public Point Position { get; set; }
        public double Altitude { get; set; }
        public string Type { get; set; }
        public string Name { get; set; }
        public string Pilot { get; set; }
        public string Group { get; set; }
        public int Coalition { get; set; }
        public int Heading { get; set; }
        public DateTime UpdatedAt { get; set; }
        public int Speed { get; set; }
        public bool Deleted { get; set; }

        public List<Unit> Units { get; } = new List<Unit>();
    }