In IssuesController.cs complete the server-side validation rule that enforces if the issue severity is "Critical" that t

using System.Web.Mvc;
using IssueReporter.Data;
using IssueReporter.Models;

namespace IssueReporter.Controllers
{
    public class IssuesController : Controller
    {
        private IssuesRepository _issuesRepository;

        public IssuesController()
        {
            _issuesRepository = new IssuesRepository();
        }

        public ActionResult Index()
        {
            return View();
        }

        public ActionResult Report()
        {
            var issue = new Issue();

            SetupDepartmentsSelectListItems();

            return View(issue);
        }

        [HttpPost]
        public ActionResult Report(Issue issue)
        {
            if (issue.Severity == Issue.SeverityLevel.Critical && string.IsNullOrEmpty(issue.Email))
            // OK I clearly do not understand overloads. Tje compiler says I require two arguments. 
            // I thoought "Index" , "Email" were my two arguments. Where to go to read and understand better?
            {
              ModelState.AddModelError("CustomError", "The item is removed from your cart");
               return RedirectToAction("Index", "Email");
            }
            else
            {
                ModelState.AddModelError(string.Empty,"The item cannot be removed");
                return View("Index");
            }

            if (ModelState.IsValid)
            {
                _issuesRepository.AddIssue(issue);

                return RedirectToAction("Index");
            }

            SetupDepartmentsSelectListItems();

            return View(issue);
        }

        private void SetupDepartmentsSelectListItems()
        {
            ViewBag.DepartmentsSelectListItems = new SelectList(
                Data.Data.Departments, "Id", "Name");
        }
    }
}