How to use Windows like filesystem action on Mac?

Hello,

Here is my issue: I have an application using an old mono version (4.4.1) on an old ide (Xamarin 6.0.1) and some Windows internal calls such as FindNext or GetFileStats. These are InternalCall methods that I need to run my application.

I have updated everything to their last version, so I am now using Visual Studio for Mac 2017 and Mono 5.18.0.249 (with their associated XamMac.dll).
When I start the application, it says that FindNext or FindFirst method is not found anymore (Missing method exception) and that my mono build is sort of broken.

So how do I replace these methods?
I need methods that give me the stats of a file (if it's hidden, etc), ones that get the next file in line in a ptr, or the first in a folder, etc.
Such as found on Windows .Net.

If anyone knows I am all ears

If I was not clear, tell me, I will try to explain the situation better.