How are C# Generics implemented?

Question

I had thought that Generics in C# were implemented such that a new class/method/what-have-you was generated, either at run-time or compile-time, when a new generic type was

Answer 1

In GenericTest<T>.Get(T), the C# compiler has already picked that object.GetHashCode should be called (virtually). There's no way this will resolve to the "new" GetHashCode method at runtime (which will have its own slot in the method-table, rather than overriding the slot for object.GetHashCode).

From Eric Lippert's What's the difference, part one: Generics are not templates, the issue is explained (the setup used is slightly different, but the lessons translate well to your scenario):

This illustrates that generics in C# are not like templates in C++. You can think of templates as a fancy-pants search-and-replace mechanism.[...] That’s not how generic types work; generic types are, well, generic. We do the overload resolution once and bake in the result. [...] The IL we’ve generated for the generic type already has the method its going to call picked out. The jitter does not say “well, I happen to know that if we asked the C# compiler to execute right now with this additional information then it would have picked a different overload. Let me rewrite the generated code to ignore the code that the C# compiler originally generated...” The jitter knows nothing about the rules of C#.

And a workaround for your desired semantics:

Now, if you do want overload resolution to be re-executed at runtime based on the runtime types of the arguments, we can do that for you; that’s what the new “dynamic” feature does in C# 4.0. Just replace “object” with “dynamic” and when you make a call involving that object, we’ll run the overload resolution algorithm at runtime and dynamically spit code that calls the method that the compiler would have picked, had it known all the runtime types at compile time.