ASP.NET MVC models when using external web services

Question

I'm getting started on a new MVC project where there are some peculiar rules and a little bit of strangeness, and it has me puzzled. Specifically, I have access to a database containing all of my data, but it has to be handled entirely through an external web service. Don't ask me why, I don't understand the reasons. That's just how it is.

So the CRUD will be handled via this API. I'm planning on creating a service layer that will wrap up all the calls, but I'm having trouble wrapping my head around the model... To create my model-based domain objects (customers, orders, so on..) should I:

1. Create them all manually
2. Create a dummy database and point an ORM at it
3. Point an ORM at the existing database but ignore the ORM's persistence in lieu of the API.

I feel like I've got all the information I need to build this out, but I'm getting caught up with the API. Any pointers or advice would be greatly appreciated.

Answer 1

Depending on the scale of what you're doing option 3 is dangerous as you're assuming the database model is the same as that exposed by the external service. Options 1 and 2 aren't IMHO much different from each other - in either case you'll have to decide what your objects, properties and behaviours are going to be - it just boils down to whether you're more comfortable doing it in classes or database tables.

The key thing is to make sure that the external service calls are hidden behind some sort of wrapper. Personally I'd then put a repository on top of that to handle querying the external service wrapper and return domain objects.

Answer 2

In general, ORMs are not known for their ability to generate clean domain model classes. ORMs are known for creating data layers, which you don't appear to need in this case.

You could probably use a code generation tool like T4 to code generate a first pass at your domain model classes, based on either the web service or the database, if that would save you time. Otherwise, you probably would just manually create the domain objects. Even if you code generate a first pass at your domain objects, it's unlikely there is a clean 1-1 mapping to your domain objects from either the database or web service, so you will likely need to spend significant time manually editing your code generated domain classes anyway.