Mono's Text Template Transformation Toolkit (T4)

At the ALT.NET Seattle conference I was introduced for the first time to the Text Template Transformation Toolkit. Also known as T4. T4 is built into Visual Studio and developers use TT to generate code from all kinds of data sources. This tutorial covers the basics.

T4 Support in MonoDevelop, with error reporting and document outline.

T4 is very much like ASP.NET in that code is mixed with output code. Additionally TT has access to data on its "host". This allows for some creative data extraction from the environments before it generates output.

To my surprise T4 thing is wildly used by lots of people. Daniel Cazzulino's company has a product just to improve Visual Studio's support for editing .tt files.

What really got me interested in T4 were the templates that Damien wrote to convert from DBML files into C# code that is suitable for use with Linq. A nice replacement for the SQLMetal tool.

I mentioned this -in passing- to Michael Hutchinson as he had been working on ASP.NET MVC support for MonoDevelop and there are some nice ASP.NET MVC T4 files out there.

In a week he implemented: the T4 command line tool, the MonoDevelop host (to support ASP.NET MVC) and he even added syntax highlighting to it (see the above screenshot).

We have also started using it to migrate the code that previously used assorted WriteLines to generate RPM files from Visual Studio/MonoDevelop projects into a nice T4 template:

Packaging Template