From time to time it is necessary to develop custom .NET code and call it from Dynamics AX. It could be that you already have the .NET code to do what you need and you don’t want to reimplement the functionality in X++, or what you are trying to do is too complex to do directly in X++.
One common situation is where you need to write a wrapper around some operating system functionality or web service to expose a much simpler API to AX.
This works, and AX has good support for calling .NET code through it’s .NET interop framework. One thing that does become more complicated is debugging, but once you know how it is actually quite easy.