Allows HttpGet decorated controllers to display model errors.

DisplayModelErrorsAttribute.cs

namespace Attributes
{
	using System.Web.Mvc;

	public class DisplayModelErrorsAttribute : ActionFilterAttribute
	{
		public override void OnActionExecuted(ActionExecutedContext filterContext)
		{
			var model = filterContext.Controller.ViewData.Model;
			var metadatas = ModelMetadataProviders.Current.GetMetadataForProperties(model, model.GetType());
			var modelState = filterContext.Controller.ViewData.ModelState;

			foreach (var metadata in metadatas)
			{
				var validator = ModelValidator.GetModelValidator(metadata, filterContext.Controller.ControllerContext);

				foreach (var error in validator.Validate(model))
				{
					var propName = metadata.PropertyName + "." + error.MemberName;
					modelState.AddModelError(propName, error.Message);
				}
			}
		}
	}
}