Ticklish Techs

As a professional software developer you will come one day to the point where you want to generate some source code or text files instead of writing it yourself. I don’t speak about dynamic web pages or big frameworks with code generation. But I bet in some of your last projects you could generate some code, too.

Maybe you do this already with a codegenerator of some kind or by using a scripting language like PHP or Python. Maybe you have reasons not to generate it and write it by yourself. Very often these reasons are bad reasons: you don’t know any adequate tool, you don’t want to buy one or you don’t have the time to learn it.

CodeSmith

The first time I had to generate source code we wanted to generate a library to access the data of an external software in a type safe way with real properties and not throwing around with strings. The input was a xml configuration file of this software.

For this aim we used a freeware code generator named CodeSmith. CodeSmith is a templating engine using C# or Visual Basic as embedded language and a syntax that is very similar to ASP. You can use all .Net framework classes and function within your template, load your own or 3rd party libraries into it and use all these classes as parameter of the template.

A few years later we had to generate code again and discovered that CodeSmith became a company that sells an enhanced standard and professional version of the well known tool. They added a very powerful IDE to create and edit your templates and for the professional version Visual Studio integration and an API to use the engine with your templates in your applications.
After buying the professional version we discovered that we cannot use CodeSmith for our needs. We wanted to build a product that generates code for the end-user on his machine but you are not allowed to distribute the CodeSmith libraries that are needed when you use the API. It took a long time for me to imagine a good usecases for an API like this if I cannot give my software away (or every user of my software has to buy a $399 licence of CodeSmith).
Fortunately the old freeware version was capable of this. It can compile your template to C# code that runs without any external reference or library. You can add this code to your application and that’s it. You do not have the fancy IDE (or you can buy a CodeSmith licence and use the IDE but process your template with the freeware version – the syntax is nearly the same) and maybe not all of the features of the new version but it is free and works. The freeware version is still downloadable on their webpage.

T4 – Text Templating Transformation Toolkit

Visual Studio 2008 (aka. Orcas) comes with its own templating engine that is a free part of every Visual Studio Professional or Team System installation (free as in: you paid for it with your Visual Studio licence). This engine is powerful with C# (or even C# 3.0) and Visual Basic as language and access the whole .Net framework and external assemblies as well.

Unfortunately there is no editor integrated in Visual Studio for the TT files. And even worse, you cannot use the engine out of the box. The DSL Tools use it but if you want to do so, you have to write code and access the public interfaces. But for both drawbacks there are solutions.

You can download a beta version of the T4 Editor. It integrates in Visual Studio (the download for the Beta 2 works fine with the final version of Visual Studio for me, too) and has syntax highlighting for template files. It comes also with some Intellisense, but only for the template syntax and not for code you write inside your templates.

Then there is TTxGen that allows you to use every file you want as input for a template in a Visual Studio solution. It adds a template to the input file and generates the output from the input using the template. It’s really that easy. TTxGen is a very lightweight thing (only 45 kByte for the installer) because it delegates most of the work to the T4 stuff from Microsoft and adds only a few menus to Visual Studio.
I had some trouble with the installation of the February 2008 CTP release. You can find my workaround at the discussions over at MSDN Code Gallery.

For one of my DSL Tools add-on libraries I use TTxGen to generate code from a xml file. Later I will post an article with the source code of the template that can be used as an example.