Petapoco - Getting return from Oracle function

I'm running into the same problem as outlined in this post:  
http://stackoverflow.com/questions/35113140/executing-oracle-function-and-getting-back-a-return-value 

I can do this in my Toad client successfully:

declare result varchar2(30);
BEGIN 
  result:=WEBUSER.F_UpdateParticipant(json input_goes here);
  dbms_output.put_line(result); 
END;

and get the return value shown in dbms_output.
This function returns:

{"Success":true} 

or 

{"Success":false} 

But I cannot get the output returned to Petapoco. I've also tried using output params like this:

var result = new Oracle.ManagedDataAccess.Client.OracleParameter("result",Oracle.ManagedDataAccess.Client.OracleDbType.Varchar2, System.Data.ParameterDirection.Output);
var sql = "DECLARE result VARCHAR2(30);" + 
          "BEGIN "+
          "    @0:=WEBUSER.F_UpdateParticipant(@1);" +
          "END;";
_db.db.Execute(sql, result, json);
res = result.ToString();

AND

var result = new Oracle.ManagedDataAccess.Client.OracleParameter("result",Oracle.ManagedDataAccess.Client.OracleDbType.Varchar2, System.Data.ParameterDirection.Output);
var sql = "DECLARE result VARCHAR2(30);" + 
          "BEGIN "+
          "    @result:=WEBUSER.F_UpdateParticipant(@1);" +
          "END;";
_db.db.Execute(sql, result, json);
res = result.ToString();

Yes, used both Execute and ExecuteScalar with same results.  
I don't really want to go back to the ADO way of doing these types of queries.