Code for calling a function in a package from C# and ODP.NET

This is my first question on this forum and I am happy to post to my own answer.

We can call an oracle package function using ODP.NET by setting CommandType.StoredProcedure.

ORA-06550: line 1, column 7:
PLS-00221: 'INSERT_FUNC' is not a procedure or is undefined
ORA-06550: line 1, column 7: PL/SQL: Statement ignored

If you get this error, just add this line as the first parameter on the command object:

cmd.Parameters.Add("Return_Value", OracleDbType.Int16,
    ParameterDirection.ReturnValue);

Here is the working code:

using (var conn = new OracleConnection(oradb))
using (var cmd = conn.CreateCommand())
{
    cmd.CommandType = CommandType.StoredProcedure;
    cmd.CommandText = "PKG_NAME.INSERT_FUNC";

    cmd.BindByName = true;

    cmd.Parameters.Add("Return_Value", OracleDbType.Int16,
        ParameterDirection.ReturnValue);
    cmd.Parameters.Add("i_description", OracleDbType.Varchar2, 1000,
        promotionEventSetupDetails.PromotionDescription,
        ParameterDirection.Input);
    cmd.Parameters.Add("i_theme", OracleDbType.Varchar2, 80,
        promotionEventSetupDetails.PromotionTheme,
        ParameterDirection.Input);
    cmd.Parameters.Add("o_id", OracleDbType.Varchar2,
        ParameterDirection.Output);
    cmd.Parameters.Add("o_error_msg", OracleDbType.Varchar2,
        ParameterDirection.Output);

    conn.Open();
    using (var dr = cmd.ExecuteReader())
    {
        // do some work here
    }
}

This must be new with a more recent version of Oracle. I was previously able to do this with the return value parameter listed after all of the input parameters in my C# code, but after running this on 12c I had this exact issue, which now works with this suggestion of putting the return val param first.