I want to render the same view after a successful action (rather than use RedirectToAction), but I need to modify the model data that is rendered to that view. The following is a contrived example that demonstrates two methods that that do not work:

    [AcceptVerbs("POST")]
    public ActionResult EditProduct(int id, [Bind(Include="UnitPrice, ProductName")]Product product) {
        NORTHWNDEntities entities = new NORTHWNDEntities();

        if (ModelState.IsValid) {
            var dbProduct = entities.ProductSet.First(p => p.ProductID == id);
            dbProduct.ProductName = product.ProductName;
            dbProduct.UnitPrice = product.UnitPrice;
            entities.SaveChanges();
        }

        /* Neither of these work */
        product.ProductName = "This has no effect";
        ViewData["ProductName"] = "This has no effect either";

        return View(product);
    }

Does anyone know what the correct method is for accomplishing this?