asp.net mvc viewmodels and fetching data in model class

Question

I have question about fetching data in view model.

For example i have viewmodel :

public class EmployeeCreateVM
{
    public Employee Employee { get; set; }
    public List<EmployeeState> EmployeeStates { get; set; } // dropdownlist data
    public List<EmployeeType> EmployeeTypes { get; set; } // dropdownlist data

    public EmployeeCreateVM()
    {
        EmployeeStates = ...
        EmployeeType = ...
    }
}

My question is about design view model, specially fetching data. For my current project, i am fetching data from controller for example :

[Get]
EmployeeCreateVM model = new EmployeeCreateVM();
model.EmployeeStates = _repository....

[Post] - again
model.EmployeeStates = _repository....

Is bad practice to fetch data directly from view model class?

Thanks

Community · Accepted Answer · 2017-05-23 12:21:12Z

1

Yes, as it violates the separation of concerns. If you later needed to change the data access methodology, it would no longer be in a single place (controller) but in each and every view model using that repository.

There is more discussion here: What to put in your ViewModel

edited May 23, 2017 at 12:21

CommunityBot

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answered Jan 11, 2012 at 13:47

Shawn

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6 Comments

Mennion Over a year ago

Thanks for interesting link. In my application i use DI, so if i change data access methodlogy, i just write other implementation my repository class and set it in di configi

wal Over a year ago

@Mennion Even so, you should not have that in the constructor; the view model (as well as all classes) should do one thing. Imagine you only wanted to return certain EmployeeTypes to your controller/view, this would require you to edit your EmployeeCreateVM class, which feels wrong.

Mennion Over a year ago

@Wal - yes, fetching data in vm class is unnatural for me. But i like DRY principle and fetching vm in get and post action is not DRY...

wal Over a year ago

@Mennion What are you repeating in your get and post actions? I suggest moving the duplicated code into EmployeeViewModelRepositoryService class or similar.

Shawn Over a year ago

@Mennion I agree. I typically use a similar service model that caches the respective dropdownlist data so that when I need to reinflate the viewmodel in cases where the POST model is invalid I don't even have to hit the repository.

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