How to render a partial view from code

protected string PartialViewToString(string viewName, object model)

{

if (string.IsNullOrEmpty(viewName)){
viewName = ControllerContext.RouteData.GetRequiredString(
"action");}
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);

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