Which reference for [Required]

Question

In Dev Express Xaf, should I be using DevExpress.ExpressApp.Model.Required or System.ComponentModel.DataAnnotations.RequiredAttribute for the [Required] attribute inside my business classes?

[Later note] I should have clarified whether it was my intent to allow the attribute to be nullable. It turns out that If I don't want it to be nullable then I need the System.ComponentModel.DataAnnotations.RequiredAttribute

Answer 1

RuleRequiredFieldAttribute

the full path being - DevExpress.Persistent.Validation.RuleRequiredFieldAttribute