protected string RenderRazorViewToString(string viewName, object model)
{
  ViewData.Model = model;
  using (var sw = new StringWriter()) {
    var viewResult = ViewEngines.Engines.FindPartialView(ControllerContext, viewName);
    var viewContext = new ViewContext(ControllerContext, viewResult.View, ViewData, TempData, sw);
    viewResult.View.Render(viewContext, sw);
    viewResult.ViewEngine.ReleaseView(ControllerContext, viewResult.View);
    return sw.GetStringBuilder().ToString();
  }
}