Question

I’ve been chugging along OK with the use of data annotations made on buddy classes so far.

When it comes to a more complex view that requires a custom view model–one that includes a few select lists, for example…would I need to then transfer my validation attributes to the view model class?

I was planning to pass the full custom view model to populate an “Edit” view, but was hoping to just receive a simple object in my “Save” action.

Where are the flaws in this plan, or is the whole thing just one big pile of fail in the first place?

Thank you.

Answer 1

You’re still validating that data that is ultimately going back into the database. So in order to keep your application DRY, you are best off to use the Buddy Classes for the original Model.

Edit
note: this doesn’t exactly have anything to do with your question

I personally prefer extend the original Model for anything “Edit” related and I prefer to use a ViewModel for “Display” only (Details pages, List pages, etc).

Example: here’s my buddy class, and in it I’ve added a “RegionName” property that I use in the Edit Page display, but it doesn’t have anything to do with the database. You can do a similar thing with custom input data that you want to validate before manipulating it into “database usable” data. I use the RegionID in the database, but I prefer to use the friendly name for the visitor instead of the ID integer

<MetadataType(GetType(UserMetaData))> _ 
Partial Public Class User 
    Public RegionName As String 
End Class 

Public Class UserMetaData 

    <DisplayName("region name")> _ 
    <Required(ErrorMessage:="region name is required.")> _  
    Public Property RegionName As String 
End Class