Reflection & System.Runtime [& self references?] about cecil HOT 3 OPEN

I'm not the Cecil author but I believe I can help here. I see people asking about this here quite often, so I suppose this should be added to the docs.

When you write something like module.ImportReference (typeof (MulticastDelegate)), you're telling Cecil to import the MulticastDelegate type from the runtime the code calling Cecil is running under.

In .NET (Core+), this means you'll get a reference to the runtime assembly defining MulticastDelegate, aka System.Private.CoreLib.

This happens to "work" in your case, but suppose you were editing a .NET Framework assembly from a .NET 7 app using Cecil, you'd still get a reference to System.Private.CoreLib, which wouldn't work under .NET Framework at all.

If you'd like to end up with a reference to System.Runtime, you'll need to use the reference assemblies instead of the implementation assemblies.

Which means you can't use the ImportReference (Type) overload, because reflection will always reference the runtime type. You need to use ImportReference (TypeReference) to do the proper thing.

I believe using ImportReference overloads with the reflection overloads such as Type/MethodReference etc is almost always a mistake, unless you're going to load the modified assembly immediately after you're done editing it. These overloads were OK when the .NET Framework was the only framework around, and the issue I described here simply couldn't occur.

So I indirectly answered your question: you can't use DefaultReflectionImporter since, as its name implies, it uses reflection, which will always get you a reference to the runtime type.

As for question 2, the root cause is the same. You're adding a reference to a type loaded at runtime to the edited assembly. Forget that the reflection overloads of ImportReference exist, and your life will get a lot easier. 🙂

from cecil.