NpgSql and PostgreSQL 12.4 - Only getting the cursor name from data reader instead of the rows of data - postgresql

Question

I'm trying to pull back data from PostgreSQL using a data reader. Each time I run my code the only value returned is the name of the refcursor.
I created the following to illustrate my problem. I'm using NpgSql .net core 3.1 aginst a PostgreSQL 12.4 database. Can anyone point out what I'm doing wrong?
Here is a simple table of cities with a function that is supposed to return the list of cities stored in the tblcities table.
CREATE TABLE public.tblcities
(
cityname character varying(100) COLLATE pg_catalog."default" NOT NULL,
state character varying(2) COLLATE pg_catalog."default",
CONSTRAINT tblcities_pkey PRIMARY KEY (cityname)
);
INSERT INTO public.tblcities(cityname, state) VALUES ('San Francisco','CA');
INSERT INTO public.tblcities(cityname, state) VALUES ('San Diego','CA');
INSERT INTO public.tblcities(cityname, state) VALUES ('Los Angeles','CA');
CREATE OR REPLACE Function getcities() RETURNS REFCURSOR
LANGUAGE 'plpgsql'
AS $BODY$
DECLARE
ref refcursor := 'city_cursor';
BEGIN
OPEN ref FOR
select *
from tblcities;
Return ref;
END;
$BODY$;
The following is the .net code.
public static void GetCities()
{
using (var cn = new NpgsqlConnection(dbconn_string))
{
if (cn.State != ConnectionState.Open)
cn.Open();
using (NpgsqlCommand cmd = cn.CreateCommand())
{
cmd.CommandText = "getcities";
cmd.Connection = cn;
cmd.CommandType = CommandType.StoredProcedure;
NpgsqlDataReader dr = cmd.ExecuteReader();
while (dr.Read())
{
//There is only one row returned when there should be 3.
//The single value returned is the name of the refcursor - 'city_cursor'
//Where are the city rows I'm expecting?
var value1 = dr[0];
}
}
}
}

Answer 1

In PostgreSQL, rather than returning a refcursor, you generally return the data itself - change the function to have RETURNS TABLE instead of RETURNS REFCURSOR (see the docs for more details). If you return a cursor to the client, the client must then perform another roundtrip to fetch the results for that cursor, whereas when returning a table directly no additional round-trip is needed.
This is one of the main reasons Npgsql doesn't automatically "dereference" cursors - lots of people coming from other databases write functions returning cursors, when in reality doing that is very rarely necessary.
For some discussions around this, see https://github.com/npgsql/npgsql/issues/1785 and https://github.com/npgsql/npgsql/issues/438.