[Solved] OracleConnection Error: One or more errors occurred. (ORA-01008: not all variables bound)

When i run this below query i got  error like one or more errors occured (ORA-01008: not all variables bound). please help me out.

                                        string sql = @"SELECT POLICY_ID,
                                            CLIENT_ID,
                                            POLICY_NUMBER,                                            
                                            GST_REFUND_AMOUNT,
                                            REMARKS,
                                            PARTNER_PAYMENT_TRANX_DATE

                                            FROM EP_FLIPKART_GSG_POLICY WHERE POLICY_ID =:POLICY_ID";

                                        using (var _db = new OracleConnection(_connectionString))
                                        {
                                            dbo = _db.QueryFirstOrDefaultAsync<FlipkartPolicyDBO>(sql, new { PROPOSAL_ID = policyId }).Result;
                                        }

thanks,

sowjanya