I needed to export Lastschriften (instructions for direct debit) for our german office, and after looking for some solutions, I realised that it is not that hard to write it yourself…
Here is the result: http://download.pokorra.de/coding/Dtaus.cs
Please feel free to use the code any way you like.
I read the input data from an XML file, of course this needs to be modified to your specific situation.
A good help was this documentation of the german DTAUS bank file format:
Another useful tool was the JDTAUS editor, a java editor that can process and create DTAUS files:
I use this to validate and test the files written with my C# program.