Question

I have a situation in which I need to extract Data Annotations information from an ASP.NET ViewModel in order to perform some more advanced validations.

Instead of writing my own type descriptor class, I wonder if I can use the native one.

Even though Data Annotations are not tied to ASP.NET MVC, if there is some ASP.NET MVC specific implementation, that wouldn’t be a problem to me.

Any ideas?

Answer 1

As I suspected, ASP.NET MVC did create a helper to class called ModelMetadata to extract meta information from model, considering data annotation attributes. See the example:

        [HttpPost]
        public ActionResult Create(AppointmentViewModel formModel)
        {
            var metaInfo = ModelMetadata.FromLambdaExpression<AppointmentViewModel, DateTime>(model => model.Date, null);
            var dateIsRequired = metaInfo.IsRequired;

            // do some logic here..

            return this.Edit(formModel);
        }

This reduces the need of manually reading the data-annotation attributes for the basic scenarios.