.NET中的选择性HTML编码（除了某些标签之外的所有内容）？

I need to display a string content (that I don't have control over) on a web page. Everything should be displayed as is except certain limited number of HTML tags (strong, em, p, br). Those should be honored and my understanding is that its safe to leave them unescaped. Everything else should be displayed as is.I need to display a string content (that I don'