The equivalent is to not make the same bad design choices the original developer made.
But, since we live in the real world, you'd shove their strings-which-contain-html into the presentation model for a particular page and then write it to the response stream.
In your Model:
public class MyPageModel
{
public string HolyCrapItsHtml {get;set;}
}
In your controller:
public ActionResult MyPage()
{
return View(new MyPageModel
{HolyCrapItsHtml = OldCode.GetHtmlICantBelieveIt()});
}
And in your page:
<div>
In the olden days, we'd concatenate our webpages together from strings like:
<%= Model.HolyCrapItsHtml %>
</div>