C# .net 如何使oracle sql 语句绑定变量

C# code

                ODC.OracleCommand cmd = conn.CreateCommand();

                cmd.CommandText = "select * from activedev where flag=:fla";

                cmd.Parameters.Add("fla",ODC.OracleDbType.NVarchar2,ParameterDirection.Input).Value="'true'";

                ODC.OracleDataReader od = cmd.ExecuteReader();

这样产生格式错误 .net 里面 绑定变量的oracle sql语句怎么写哈 求帮助

------解决方案--------------------
OracleConnection oraCon = new OracleConnection("data source=test;user id=test;password=test");
OracleCommand oraCmd = new OracleCommand("select * from tb where id=:id", oraCon);
OracleParameter oraPara = new OracleParameter("id", OracleType.NVarChar);
oraPara.Direction = ParameterDirection.Input;
oraPara.Value = "001";
oraCmd.Parameters.Add(oraPara);
oraCon.Open();
OracleDataReader oraRdr = oraCmd.ExecuteReader(CommandBehavior.CloseConnection);
oraRdr.Read();
Response.Write(oraRdr[0].ToString());
oraRdr.Close();
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