C# Calling PACKAGE.PROCEDURE with OUT parameter

Question

From C# Code, I'm trying to call a PACKAGE.PROCEDURE() from Oracle. In this simple example I should get one value from the procedure call, but all I get is error:

> wrong number or types of arguments in call to 'RETURN_NUM'

The procedure is declared as follows:

PROCEDURE return_num(xNum OUT NUMBER) AS
BEGIN
xNum:= 50;
dbms_output.put_line('hello world ' || xNum);
END;

C# code:

Oraclecon.Open();
OleDbCommand myCMD = new OleDbCommand("TEST.return_num", Oraclecon);
myCMD.CommandType = CommandType.StoredProcedure;
myCMD.Parameters.Add("xNum", OleDbType.Numeric);
OleDbDataReader myReader;
myReader = myCMD.ExecuteReader();

Can some one please point out what I'm doing wrong. Then in a real scenario I would like to call a procedure that returns a set of values from a custom Type, such as:

TYPE r_interface_data IS RECORD
(
object_id VARCHAR2(16),
obj_type VARCHAR2(32)
);
TYPE t_interfase_data IS TABLE OF r_interface_data;

How can I approach that. Thanks!