MVC DropDownListFor-选定值ViewModel类

Question

I am trying populate the selected value of a dropdown list. When I set the selected value on my ViewModel as a string, it works perfectly. When I set the selected value property as part of a subclass, it fails:

@Html.DropDownListFor(model => model.JMASettings.CustomerID, Model.CustomerIDList)

This method works:

@Html.DropDownListFor(model => model.CustomerID, Model.CustomerIDList)

1. Is it OK to have classes inside of the ViewModel?

    public class SettingsViewModel { public SettingsViewModel() { JMASettings = new JMASettings(); } public JMASettings JMASettings {get; set;} } public class JMASettings { public string CustomerID {get; set;} } 

2. Do you recommend that I copy and paste the contents of JMASettings into my settings view model class?

Answer 1

1. Sure. Your view model can contain whatever you like.

2. Not necessarily. There's no functional reason your first attempt using model.JMASettings.CustomerID shouldn't show the selected value. If it's not, then there's some other problem. You may not be properly populating the CustomerID property on JMASettings instance, or something in ModelState may be overriding what you set. ModelState is composed of values from Request , ViewData and ViewBag , first , and only values from Model as a last resort.

Answer 2

Is it OK to have classes inside of the ViewModel?

Yes it is OK, but probably not necessary.

Do you recommend that I copy and paste the contents of JMASettings into my settings view model class?

Yes I recommend to move it to a single model as the subclass will require you to create a custom model binder.