Question

I have a web client that calls my WCF business service layer, which in turn, calls external WCF services to get the actual data. Initially, I thought I would use DTOs and have separate business entities in the different layers… but I’m finding that the trivial examples advocating for DTOs, to be, well, trivial. I see too much duplicate code and not much benefit.

Consider my Domain:

Example Domain
I have a single UI screen (Asp.net MVC View) that shows a patient’s list of medications, the adverse reactions (between medications), and any clinical conditions (like depression or hypertension) the patient may have. My domain model starts at the top level with:

   MedicationRecord
      List<MedicationProfile> MedicationProfiles
      List<AdverseReactions> Reactions
      List<ClinicalConditions> ClinicalConditions

   MedicationProfile is itself a complex object
      string Name
      decimal Dosage
      Practitioner prescriber 

   Practioner is itself a complex object
      string FirstName
      string LastName
      PractionerType PractionerType
      PractionerId Id
      Address Address    

      etc.

Further, when making the WCF requests, we have a request/response object, e.g.

   MedicationRecordResponse
      MedicationRecord MedicationRecord
      List<ClientMessage> Messages
      QueryStatus Status

   and again, these other objects are complex objects
   (and further, complicates matter is that they exist in a different, common shared namespace)

At this point, my inclination is that the MedicationRecordResponse is my DTO. But in pure DataContracts and DTO and separation of design, am I suppose to do this?

   MedicationRecordResponseDto
      MedicationRecordDto
      List<ClientMessageDto> 
      QueryStatusDto

   and that would mean I then need to do
      MedicationProfileDto
      PractitionerDto
      PractitionerTypeDto
      AddressDto
   etc.

Because I have show almost all the information on the screen, I am effectively creating 1 DTO for each domain object I have.

My question is — what would you do? Would you go ahead and create all these DTOs? Or would you just share your domain model in a separate assembly?

Here’s some reading from other questions that seemed relevant:

1. WCF contract know the domain
2. Alternatives for Translation Layer in SOA: WCF
3. SOA Question: Exposing Entities

Answer 1

Take a look on excellent articles

• Why You Shouldn’t Expose Your Entities Through Your Services
• DTO’s Should Transfer Data, Not Entities

above links don’t work, looks like a domain issue (I hope it’ll be fix), here is the source:

• DTO’s Should Transfer Data, Not Entities
• Why You Shouldn’t Expose Your Entities Through Your Services