var connection = "host=localhost;database=message_db;password=postgres;username=postgres";

var message = new Message
{
    Subject = "subject",
    BodyHtml = "Html",
    BodyText = "Text"
};

var recipients = new List<Recipient>
{
    new Recipient {Address = "jake@bob.com", Name = "Jake Scott", RecipientTypeId = 1},
    new Recipient {Address = "ben@example.com", Name = "Ben Scott", RecipientTypeId = 2},
    new Recipient {Address = "suki@example.com", Name = "Ben Scott", RecipientTypeId = 3},
};

NpgsqlConnection.MapCompositeGlobally<Message>("message_dto");
NpgsqlConnection.MapCompositeGlobally<Recipient>("recipient_dto");

using (var connection = new NpgsqlConnection(connectionString))
{
    connection.Open();

    connection.Execute("delete from recipient;");
    connection.Execute("delete from address;");
    connection.Execute("delete from message;");


    NpgsqlCommand command = connection.CreateCommand();

    command.CommandType = CommandType.StoredProcedure;
    command.CommandText = "create_message";
    command.Parameters.AddWithValue("message", message);
    command.Parameters.AddWithValue("recipients", recipients);

    using (NpgsqlDataReader reader = command.ExecuteReader())
    {
        reader.Read();
        var messageId = reader.GetInt64(0);
        Log.Information("MessageId: {messageId}", messageId);
    }
}