With this
PROCEDURE \"ADD_BOOKMARK_GROUP\" ( \"NAME\" IN VARCHAR2, \"BOOKMARK_GROUP_ID\" IN NUMBER, \"STAFF_ID\" IN VARCHAR2, \"MAX_NO\" IN INT,
You can probably set the BindByName parameter on the OracleCommand object. This works for straight SQL queries with parameters, I've not tried it with stored procedures but it would be logical...
cmd.BindByName = true;