MVC4 RenderViewToString不尊重移动视图

I'm building mobile views for an asp.net MVC4 site and have encountered a problem. We have quite a bit of places where we have a method to convert a view into a string but this method doesn't seem to work with displaymodes thus always finding the default view. E.g. index.cshtml instead of index.mobile.cshtml.I'm building mobile views for an asp.net MVC4 s