.net core call oracle function put returned value in first parameter - oracle

Question

.net core 3.1
nuget: Oracle.ManagedDataAccess.Core 2.19.91
Oracle function:
create or replace NONEDITIONABLE FUNCTION GET_TOTAL_SALES
(
PARAM1 IN VARCHAR2,
PARAM2 IN VARCHAR2
)
RETURN VARCHAR2 AS
BEGIN
RETURN 'abc';
END GET_TOTAL_SALES;
.net core code:
var cmdText = "GET_TOTAL_SALES";
using (var connection = new OracleConnection(connStr))
{
using (var command = new OracleCommand(cmdText, connection))
{
connection.Open();
command.CommandType = CommandType.StoredProcedure;
var param1 = new OracleParameter("PARAM1", OracleDbType.Varchar2);
param1.Direction = ParameterDirection.Input;
param1.Value = "param1Value";
command.Parameters.Add(param1);
var param2 = new OracleParameter("PARAM2", OracleDbType.Varchar2);
param2.Direction = ParameterDirection.Input;
param2.Value = "param2Value";
command.Parameters.Add(param2);
var returnValue = new OracleParameter("returnValue", OracleDbType.Varchar2);
returnValue.Direction = ParameterDirection.ReturnValue;
command.Parameters.Add(returnValue);
command.ExecuteNonQuery();
Console.WriteLine(returnValue.Value); //""
Console.WriteLine(param1.Value); //"abc"
}
}
The result is that the returned value is putted into the first parameter (param1) and not into the returnValue. Why? Help!

Answer 1

I asked Oracle and got a reply:
"This is expected behavior. The first parameter bound for a function must be the return value. From the doc:
https://docs.oracle.com/en/database/oracle/oracle-data-access-components/19.3.2/odpnt/featOraCommand.html
I know, it is crazy.
We can also use binding by name:
command.BindByName = true;
and then order doesn't matter.