CODEWITHSUNDEEP
asp.netdesign-patterns
user386167
user386167

Reputation:

Passing ViewModel from Presentation to Service - Is it Okay?

In one of my views, I have a ViewModel which I populate from two tables, and then bind a List<ViewModel> to an editable GridView (ASP.NET Web Forms).

Now I need to send that edited List<ViewModel> back to the Services layer to update it in the database.

My question is - is it Okay to send the ViewModel back to Services, or should it stay in the Presentation? If not - should I better use a DTO? Many thanks.

Upvotes: 10

Views: 1524

Answers (3)

Gert Arnold
Gert Arnold

Reputation: 109185

I would not do it. My rule is: supply service methods with everything they need to do their job and nothing more.

Why?

  1. Because it reduces coupling. More often than not service methods are addressed from several sources (consumers). It is much easier for a consumer to fulfil a simple method signature than having to build a relatively complex object like a view model that it otherwise may have nothing to do with. It may even need a reference to an assembly it wouldn't need otherwise.

  2. It greatly reduces maintenance effort. I think an average developer spends more than 50% of his time inspecting and tracking existing code (maybe even much more). Now everybody knows that looking for something that is not there takes disproportionally much time: you must have been everywhere to be sure. If a method receives arguments (or object with properties) that are not used directly or further down the call stack you or others will walk this long road time and again.

So if there is anything in the view model that does not play a part in the service method, don't use it to call the method.

Upvotes: 9

christophe.chapron
christophe.chapron

Reputation: 423

Nice question !

After several (hard) debates with my teammates + my experience with MVC applications, I would not recommend to pass viewmodel to your service / domain layer.

  1. ViewModel belongs to presentation, no matter what.
  2. Because viewModel can be a combination of different models (e.g : 1 viewModel built from 10 models), your service layer should only work with your domain entities.

Otherwise, your service layer will end up to be unusable because constrained by your viewModels which are specifics for one view.

Nice tools like https://github.com/AutoMapper/AutoMapper were made to make the mapping job.

Upvotes: 12

NoWar
NoWar

Reputation: 37632

Yes. I am pretty sure it is ok.

Try to use MS Entity Framework and it will help you allots.

Upvotes: -3

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