I was really happy back in January when I learned that you can now can import CSV, and other flat files, into AX using AIF with .NET transformations. Many proprietary file imports, and exports, can now be handled by AIF allowing you to focus on the business logic rather than the nitty-gritty file handling stuff.

But since then I have missed proper documentation on how you actually go about it. The article "Walkthrough: Creating a .NET Assembly Transform" on MSDN, doesn't quite get you to the finish line, where you have a file the AIF can actually read.

Today however I found a three part blog series where part 3 ends up in having a file that AIF will consume.

I recommend that you read all three parts you want to play with these transformations. Here's the link to part 1:
http://shashidotnet.wordpress.com/2011/04/11/dynamics-ax-2012-aif-import-csv-file-part-1-consume-web-service/