I'm Getting 'Ora-01745: Invalid Host/Bind Variable Name' When I Add Data In To My Oracle Database

public void AddNDADetails(string id)
       {
           try
           {
               con = db.CreateConnection();
               con.Open();

               string query = string.Format("INSERT INTO NDAInformation (NDAID,RegNumber,DateCreate,RefName,ReqServ,ServDetails) VALUES (:ndaID,:regnumber,TO_DATE(:date,'DDMMYYYY'),:refname,:regserv,:servdetails)");
               //string query = string.Format("INSERT INTO NDAInformation (NDAid,RegNumber,DateCreate,RefName,ReqServ,ServDetails) VALUES ('{0}', '{1}',TO_DATE('{2}','DDMMYYYY'), '{3}','{4}','{5}')", id, om.RegNumber, om.Date, om.ComRef, om.ComService, string.Join(",", om.ReqServiceDetails));
               cmd = db.GetSqlStringCommand(query);
               cmd = con.CreateCommand();
               cmd.CommandText = query;

               db.AddInParameter(cmd, "ndaID", DbType.String, id);
               db.AddInParameter(cmd, "regnumber", DbType.String, om.RegNumber);
               db.AddInParameter(cmd, "date", DbType.Date, om.Date);
               db.AddInParameter(cmd, "refname", DbType.String, om.ComRef);
               db.AddInParameter(cmd, "regserv", DbType.String, om.ComService);
               db.AddInParameter(cmd, "servdetails", DbType.String, string.Join(",", om.ReqServiceDetails));
               db.ExecuteNonQuery(cmd);

           }

           catch (Exception ex)
           {
               throw ex;
           }
       }