在MVC4中定义自定义数据类型的正则表达式验证

I upgraded a project from MVC3 to MVC4 and noticed that one of my validators wasn't triggering anymore. I chased it down to a custom DataType in the Shared/EditorTemplates folder that is used for capturing Social Security numbers in various forms across the site. (We only show the last 4 digits when the page is loaded after a save, to explain the regex.) I upgraded a project from MVC3 to MVC4 and noti