Where to put extra view data that doesnt relate to view data

Question

So, lets look at an example. I have a Customer view model that looks like this:

public class CustomerViewModel {
    public string Name {get; set;}
    public int CustomerTypeId {get; set;}
}

On the UI there needs to be a drop down of customer types. In order to populate this, something needs to go to the business layer or data layer and grab this list of customer types.

It seems to me that this logic doesn't really belong in CustomerViewModel since it isn't really customer data; only CustomerTypeId is. So my question is, where in general (not necessarily in .net MVC, but general practice for the MVC view model concept) do people put this data access?

Is it acceptable to have a function in the view model itself called GetCustomerTypes()?

public class CustomerViewModel {
    public string Name {get; set;}
    public int CustomerTypeId {get; set;}

    public List<CustomerType> GetCustomerTypes() { ... }
}

Should I make a class/method in the business layer or a helper and import the code manually in the view to access this function? It seems to me like this would be code that clutters up the view and doesn't belong there.

@{
    using My.App.CustomerTypeHelper;
    var helper = new CustomerTypeHelper();
    var customerTypes = helper.GetCustomerTypes();
}

...

@Html.DropDownFor(x => x.CustomerTypeId, customerTypes)

The global Html helper eases this problem a bit in .Net, but I am looking for a more global solution conceptually that I can apply to PHP code, etc also. PHP doesn't have the ability to cleanly have a static class that can be separated into small organized units with extension methods. So any global helper is likely to get large and ugly.

Answer 1

You should include List<CustomerType> in the model but do NOT implement function inside the model. Set the data from controller instead.

Something like this:

public class CustomerViewModel {
    public string Name {get; set;}
    public int CustomerTypeId {get; set;}

    public List<CustomerType> CustomerTypes { get; set; }
}

Assign data to ViewModel from Controller:

var model = new CustomerViewModel();
model.CustomerTypes = Customer.GetCustomerTypes();