CREATE OR REPLACE FUNCTION public.test_get_users2 (
  userid integer
)
RETURNS SETOF refcursor AS
$body$
DECLARE 
    ref1 refcursor :='ref1';
    ref2 refcursor :='ref2';
    ref3 refcursor :='ref3';
BEGIN
	OPEN ref1 FOR 
		SELECT user_id, user_name,* FROM users;
	RETURN NEXT ref1;

	OPEN ref2 FOR 
		SELECT id, company FROM customers;
	RETURN next ref2;

	OPEN ref3 FOR 
		SELECT id, forename, surname, company FROM suppliers;
	RETURN next ref3;
END;
$body$
LANGUAGE 'plpgsql';

                    sql = @"DO LANGUAGE plpgsql $$ DECLARE
                                BEGIN
                                 SELECT test_get_users(0);
                                 FETCH ALL IN ""ref1"";
                                 FETCH ALL IN ""ref2"";
                                 FETCH ALL IN ""ref3"";
                            END $$;";
                    // Start a transaction as it is required to work with cursors in PostgreSQL
                    NpgsqlTransaction tran = connection.BeginTransaction();

                    using (NpgsqlCommand command =
                       new NpgsqlCommand(sql, connection))
                    {
                        command.CommandType = CommandType.Text;//.StoredProcedure;
                        var dr = command.ExecuteReader();
                        while (dr.Read())
                        {
                            Console.Write("{0}\n", dr[0]); // здесь показывает имена всех наборов
                        }
                        // Switch to the second result set
                        dr.NextResult();

                        // Output the rows of the second result set - здесь уже читать нечего
                        while (dr.Read())
                            Console.Write("{0}\t{1} \n", dr[0], dr[1]);