Can a developer write code in .NET and then UFT can communicate with it through .NET and not the front end of the application?
Can UFT make calls to .NET functionality?
My question is vague but my knowledge on the topic is vague.
The answer is yes. But i'll need more details of what you want to do exactly.
I can tell you from experience I have done similar things. For example, I've built test hooks in these ways in the past.
* Using their SDK to expose automation properties to the automation tool. (I did this in RFT, but QTP has a similar feature from my research) Go gaga over testing: Steps to use the QTP .NET Extensibility sdk
* You can do it in a tool agnostic way. A good way is to use a lightweight web server that just translate REST/http requests into either Windows UI Message/Event (for UI automation) or directly hook and call methods in the application under test.