为什么对Oracle（View）的这种选择查询不起作用？

Question

First I tested simple cases:

cmd.Parameters.Add(new OracleParameter(":paramCode", OracleDbType.NVarchar2)).Value = userCode;
cmd.CommandText = "SELECT * FROM VIEWUSERDATA WHERE  Codigo = :paramCode";
cmd.CommandType = System.Data.CommandType.Text;
OracleDataReader reader = cmd.ExecuteReader();
while (reader.Read())
{
    //Works, retrieve data
}

Another:

cmd.Parameters.Add(new OracleParameter(":paramRole", OracleDbType.NVarchar2)).Value = userRole;
cmd.CommandText = "SELECT * FROM VIEWUSERDATA WHERE  Role = :paramRole";
...
while (reader.Read())
{
    //Also works
}

But when join, doesn't work.

cmd.Parameters.Add(new OracleParameter(":paramCode", OracleDbType.NVarchar2)).Value = userCode;
cmd.Parameters.Add(new OracleParameter(":paramRole", OracleDbType.NVarchar2)).Value = userRole;
cmd.CommandText = "SELECT * FROM VIEWUSERDATA WHERE Role = :paramRole AND Code = :paramCode";
...
while (reader.Read())//don't retrieve anything
{
}

Data exists, If I do the query in an external query editor(window) works fine.

Thanks.

Answer 1

By default, Oracle parameter binding is by position, not by name. Either swap the two cmd.Parameters.Add calls or set cmd.BindByName = true; before executing the query.