Why F#?

As a 20+ year C# developer I’ve tried several times to learn/use F#. Despite being interested in FP, my brain is having trouble figuring out how to structure my code in F#. In C# I’d either build a service (or use the mediator pattern) for the domain and a repository for data access. With F# it’s functions all the way down and it feels unnatural (as silly as that may sound).

The secret is currying. Replace your DI for currying and you'll start to see somewhat similar patterns

along with what jcmontx said: F# is structured bottom from top. As in you can't reference something that is later defined earlier. I find that naturally leads to getting a decent enough structure "for free" because it forces you to have your basic functionality early on and build on that later.

That also, IMO, makes untangling/splitting up parts of the codebase easier as well.

By the way, I consider https://www.bartoszsypytkowski.com/dealing-with-complex-depe... to be the canonically correct way to do DI when you want to inject more than like two dependencies.

That makes sense when one is used to the Visual Studio organization of solutions and projects, with some main method somewhere being the entry point, unless it's a WCF service or somesuch that gets run via a service manager.

I only used F# at its command line, fsi.exe, to give me commandline access to .NET for exploration, testing, and munging data. Over time, I built up quite a library of usable functions that I'd have the fsi.exe program pre-load when I kicked it off, leaving me at the prompt with all .NET namespaces and my code ready and accessible.

Once you get access to your database's data, it's easy to write queries against it and then play with the data. I could then port the F# processing bits that worked into my C# projects as necessary, but it was far easier to do it that way than to write the logic deep within complex multi-project solution files, where the various classes are spread throughout the projects' files.

I also just really enjoyed using F#.

Have you tried using a book or a tutorial to see how things can be done using idiomatic F#?