System.ComponentModel.DataAnnotations.compare vs System.Web.Mvc.Compare

Question

MVC 4 Beta project fails to compile after upgrading to .Net 4.5.

This happens due to conflict between System.ComponentModel.DataAnnotations.CompareAttribute

Answer 1

Vinney nailed most of it with the exception of which one you should use...

The reason you have a conflict after changing your target framework to 4.5 is because prior to .NET 4.5 there was no CompareAttribute class in the System.ComponentModel.DataAnnotations namespace and the class defined under System.Web.Mvc filled the gap. Therefore, as an example if you were using [Compare] and [Required] attributes in your model class prior to updating your target framework you ended up with a conflict when you upgraded.

Assuming you are not using anything else in the System.Web.Mvc namespace in your model class, you should remove that using statement and let it rely on the System.ComponentModel.DataAnnotations namespace. Unobtrusive client-side validation will continue to work exactly as it did before, just as it does for other attributes that you decorate your model's properties with from the same namespace (eg Required).