สอบถามปัญหา class OracleDataReader ของฐานข้อมูล Oracle เกี่ยวกับการใช้งานอย่างไร ฟ้อง Error

public OracleDataReader QueryDataReaderLoginOracle(
        string SQL,
        string id,
        string password)
        {
            OracleParameter oraParameter1 = new OracleParameter(":user", OracleType.VarChar,100);
            OracleParameter oraParameter2 = new OracleParameter(":password", OracleType.VarChar,100);        
            this.objConn_ora = new OracleConnection();
            

            OracleCommand oraCommand = new OracleCommand();
            if (this.objConn_ora.State == ConnectionState.Open)
                this.objConn_ora.Close();
            this.objConn_ora.ConnectionString = this.StrConn;
            try
            {
                this.objConn_ora.Open();
                oraCommand.CommandType = CommandType.Text;
                oraCommand.CommandText = SQL;
                oraCommand.Connection = this.objConn_ora;
                oraCommand.Parameters.Add(oraParameter1).Value = (object)id;
                oraCommand.Parameters.Add(oraParameter2).Value = (object)password;               
            }
            catch (Exception ex)
            {
                this.Close();
                System.Console.WriteLine("Exception");
            }
            return oraCommand.ExecuteReader();
        }

StringBuilder Loginuser = new StringBuilder();
Loginuser.Append("select * from user where username=:user And password=:password");
string SQL = Loginuser.ToString();
OracleDataReader odr = DB.QueryDataReaderLoginOracle(SQL,txtUser.Text,txtPass.Text);