Here are some additional resources so that you can delve deeper into the realms of C# functional programming:
- Functional C# by Wisnu Anggoro: https://www.packtpub.com/application-development/functional-c. This book is devoted to C# functional programming and is a good place to start if you want to know more.
- Functional Programming in C# by Jovan Poppavic (MSFT): https://www.codeproject.com/Articles/375166/Functional-programming-in-Csharp. This is an in-depth article on functional C# programming. It contains diagrams and has a 5-star rating.