When trying out these tutorials (T4 Tutorial: Creating reusable code generation templates) I noticed that although I was using plain c# I didn't get any intellisense, probably because of the file extension (.tt)
Isn't there anyway to say to Visual Studio to consider those .tt files as .cs files and thus get the correct intellisense help?
You can just download tangible's T4 Editor at t4editor.tangible-engineering.com it has Intelli-Sense for most important namespaces also in the FREE EDITION.
You can purchase the professional version of T4 Editor. It works very well in standalone .tt files, but unfortunately, due to the differences in how the pro version of T4 Editor and T4 itself compile the templates, you will get false errors reported for this tutorial, which relies on T4 Toolbox.
As Scott Hanselman also points out, the intellisense you might be expecting from some of the videos and articles on T4 are not built in to VS2008, you need the T4 Editor from Clarius, but they do have a community edition with some minimalist features to get you started.
I found the devart T4 editor has all the features I was looking for in a Visual Studio Extension for free. It's all native. Feels like editing any other source file.
For some reasons, I couldn't install the extensions mentionned in the other answers. My solution was to use Visual Studio Code to edit the .tt files. VS Code has some good t4 synthax highlighter plugins.
