ModelState.IsValid may be used to sanity check models on the C# side.

I refined the Controller I wrote here to make it so one could navigate to /Home/InvalidTest/ and pass an inappropriate Person object (in this case, a Person who lived to be 132 years old). ModelState.IsValid may be used to sanity check models on the C# side beyond what @Html.ValidationMessageFor may do in a View, and here I use it to catch the oddity of an 132-year-old Person.

using System;
using System.Web.Mvc;
using KeepFeelingValidation.Models;
namespace KeepFeelingValidation.Controllers
{
   public class HomeController : Controller
   {
      public ActionResult Index()
      {
         Person person = new Person();
         person.Name = "Adolph Coors I";
         person.AgeAtDeath = 82;
         person.BirthDay = new DateTime(1847, 2, 4);
         person.IsCrazy = true;
         person.Id = Guid.NewGuid();
         return View(person);
      }
      
      public ActionResult About(Person person)
      {
         if (ModelState.IsValid) return View();
         return View("Invalid");
      }
      
      public ActionResult Invalid()
      {
         return View();
      }
      
      public ActionResult InvalidTest()
      {
         Person person = new Person();
         person.Name = "Adolph Coors I";
         person.AgeAtDeath = 132;
         person.BirthDay = new DateTime(1847, 2, 4);
         person.IsCrazy = true;
         person.Id = Guid.NewGuid();
         return RedirectToAction("About", "Home", person);
      }
   }
}

 
 

If I set a breakpoint at return View("Invalid"); and run the debugger, I can tell that a collection is attached to ModelState containing:

1. metadata for each of the fields to validate
2. and if the validations went less-than-lovely for each of the given fields

Yay!