Mono.Cecil VS Harmony

You mean Mono Cecil, native IL Emit or Reflection.Emit, or maybe LINQ Expressions?

Here's the documentation from a library in a project I'm working on right now: https://github.com/jbevain/cecil/wiki/

Some more details https://github.com/pardeike/Harmony/issues/424

Here's what you're looking for.

Probably a little out of your scope but the library Harmony you can write patches (detours) on methods. Using get/set instead of a field would allow you to override the property's method. Let's say you wanted to write something to always have the name uppercase. You could patch the constructor and set this.name = this.name.ToUpper() but that field is publicly assignable so you can't really enforce that. On the other hand with a property you can override the set method to say this._name = value.ToUpper().

It's kind of a subtle distinction that I think was lost between the posted article and the original article it was responding to, but I don't think the kinds of reflection capabilities that Roslyn provides is what the author intended. The specific example given in the referenced article for "Higher-order programs" specifically refers to the ability to replace function implementations at runtime without interrupting the program, and specifically calls out hot-code reloading (such as what Java provides) as a deficient form of similar functionality. This is closer to the type of functionality libraries like Harmony provide, but even that solution requires including the library and instrumenting your code ahead of time.

https://github.com/pardeike/Harmony harmony lets you patch functions at runtime, kind of like a dll injection / memory edit

Download Harmony 2 and put net472 version of the library into GordianQuest_Data\Managed

I'd recommend looking into Harmomy and seeing if you're able to use it. It makes modifying DLLs pretty convenient.