RenderViewToString.cs

/* 
* Original Sample: http://craftycodeblog.com/2010/05/15/asp-net-mvc-render-partial-view-to-string/ 
*/

public class HomeController : Controller
    {
        public ActionResult Index()
        {
            string MyModelData = "";

            var teste = RenderPartialViewToString("About", MyModelData);           
           
            return View();
        }

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


        protected string RenderPartialViewToString(string viewName, object model)
        {
            if (string.IsNullOrEmpty(viewName))
                viewName = ControllerContext.RouteData.GetRequiredString("action");

            ViewData.Model = model;

            using (StringWriter sw = new StringWriter())
            {
                ViewEngineResult viewResult = ViewEngines.Engines.FindPartialView(ControllerContext, viewName);
                ViewContext viewContext = new ViewContext(ControllerContext, viewResult.View, ViewData, TempData, sw);
                viewResult.View.Render(viewContext, sw);

                return sw.GetStringBuilder().ToString();
            }
        }
    }

Forking for safe keeping.