Render a partial razor view to a string. Can't remember where this code came from originally (it isn't mine)

gistfile1.cs

      private static string RenderPartialViewToString(Controller controller, string pathToView, object viewModel,
                                                     ViewDataDictionary viewData = null) {
         String result;
         var viewEngine = ViewEngines.Engines.FindPartialView(controller.ControllerContext, pathToView);

         using (var writer = new StringWriter()) {
            var vd = viewData == null  ? new ViewDataDictionary(viewModel)
                                       : new ViewDataDictionary(viewData) { Model = viewModel };
            var viewContext = new ViewContext(controller.ControllerContext,
                                                      viewEngine.View,
                                                      vd,
                                                      new TempDataDictionary(), writer);
            viewEngine.View.Render(viewContext, writer);
            result = writer.ToString();
         }
         return result;
      }