I've done the same. The problem isn't C#'s access to the APIs, the problem is the APIs are incomplete, especially as MS moved to the SDI interface since Office

I've done the same. The problem isn't C#'s access to the APIs, the problem is the APIs are incomplete, especially as MS moved to the SDI interface since Office 2010. There are somethings you just can't do in an Add-In that are obviously possible due to built-in features. Things like have a text-box in a toolbar show the proper text in inactive windows.