Question

Here is a description (ASP.NET MVC 3):

1. I have this parameter DataAnnotationsModelValidatorProvider.AddImplicitRequiredAttributeForValueTypes in the default value true (checked with the debugger)

2. I have value-type field in my model (int, DateTime, decimal):

   public class MyModel
   {    
      public int SomeField { get; set; }
   }
   

3. When I post empty form to this action (no SomeField specified):

     public ActionResult Submit(MyModel request)
     { 
         if (ModelState.IsValid)
         {
             ..
         }
     else
         {
             ..
         }
      }
   

4. I don’t have any validation errors! It seems to me logical — the default value of int is 0. Which is a value.

Questions:

If I want to force this value always expicitly set in request I should make it nullable and put [Required] on it, this works. But what DataAnnotationsModelValidatorProvider.AddImplicitRequiredAttributeForValueTypes is for?

Answer 1

If we refer to ASP.NET MVC sources, DataAnnotationsModelValidatorProvider.AddImplicitRequiredAttributeForValueTypes is checked only in DataAnnotationsModelValidatorProvider.Getvalidators method which provides validation metadata for HTML Helpers (when rendering data-val-* attributes) and DefaultModelBinder.

So, DataAnnotationsModelValidatorProvider.AddImplicitRequiredAttributeForValueTypes could be set when there is need to change behaviour of client-side validation and allow passing empty values(i.e. field is posted but has no value set) for value types to controller action.