Last year I wrote a Language Service for Visual Studio which added syntax highlighting for NHaml files: http://github.com/snappycode/hamleditor.
To clarify, NHaml is a html template language that can mix in code elements like an aspx file can. This plugin adds support to the IDE for editing NHaml files, but basically only adds syntax highlighting.
I was wondering if anyone knows how to add inline c# intellisense to the service like you get now in an aspx file. I'm hoping that would be possible without doing the whole c# grammar myself specific for the plugin.
Has anyone written a language service that mixes languages?
UPDATE: It looks like the spark view engine guys have made some inroads here, I am investigating their implementation