wimlib

Thank you very much.
I was able to use that code as reference to write C# code to add or remove compression from files.
I used to call Compact.exe, but now I can skip that part.

My project is a C# program where you give it a directory, and it recursively compresses files, but first checks if the ...

Is it known how to replicate the effect of Compact.exe, and cause LZX compression to be applied to files?

I was looking at what Compact.exe did, but only really noticed two calls to DeviceIoControl, one with FSCTL_GET_EXTERNAL_BACKING and one with FSCTL_SET_EXTERNAL_BACKING.