using System.Web.Mvc;

namespace TestMvcPRG.Helper
{
    public class Redirect303 : ActionResult
    {
        private string _url;

        public Redirect303(string url)
        {
            _url = url;
        }

        public override void ExecuteResult(ControllerContext context)
        {
            context.HttpContext.Response.StatusCode = 303; // redirect using GET
            context.HttpContext.Response.RedirectLocation = _url;
        }
    }

    public abstract class BaseController : Controller
    {
        public Redirect303 Redirect303(string actionName)
        {
            return new Redirect303(Url.Action(actionName));
        }

        public Redirect303 Redirect303(string actionName, object routeValues)
        {
            return new Redirect303(Url.Action(actionName, routeValues));
        }

        public Redirect303 Redirect303(string actionName, string controllerName)
        {
            return new Redirect303(Url.Action(actionName, controllerName));
        }

        public Redirect303 Redirect303(string actionName, string controllerName, object routeValues)
        {
            return new Redirect303(Url.Action(actionName, controllerName, routeValues));
        }
    }
}

using System.Web.Mvc;
using TestMvcRPG.Helper;

namespace TestMvcPRG.Controllers
{
    public class HomeController : BaseController
    {
        [HttpGet]
        public ActionResult Index()
        {
            return View();
        }

        [HttpPost]
        public ActionResult Index(string data)
        {
            if (ModelState.IsValid)
            {
                return Redirect303("Index"); // post-redirect-get
            }
            return View();
        }
    }
}