This is all very basic, instead you can use C#'s new static interface methods feature to create higher-kinded traits where you can properly generalise over a monad trait (or applicatives, functors, foldables, etc.), which is what I do in language-ext [0].

I'm not saying that implementing SelectMany for specific data-types isn't valuable. It certainly ends up with more elegant and maintainable code, but the true power of monads and other pure-FP patterns opens up when you can fully generalise.

* I have a blog series on it that covers implementing Semigroups, Monoids, Functors, Foldables, Traversables, Applicatives, Monads, and Monad Transformers (in C#) [1]

* The monad episode (my 'Yet Another Monad Tutorial') [2]

* An entire app generalised over any monad where the monad must support specific traits [3]. It's the program I use to send out the newsletters from my blog.

Happy to answer any questions on it.

[0] https://github.com/louthy/language-ext/

[1] https://paullouth.com/higher-kinds-in-c-with-language-ext/

[2] https://paullouth.com/higher-kinds-in-csharp-with-language-e...

[3] https://github.com/louthy/language-ext/tree/main/Samples/New...