It is Url.Content:
ASPX:
<link rel="stylesheet" href="https://stackoverflow.com/questions/2452931/<%= Url.Content("https://stackoverflow.com/questions/2452931/~/Content/style.css") %>" type="text/css" />
Razor:
<link rel="stylesheet" href="https://stackoverflow.com/questions/2452931/@Url.Content("https://stackoverflow.com/questions/2452931/~/Content/style.css")" type="text/css" />