Looking up FieldRef and FieldDef metadata tokens via Reflection

Question

I'm working on a program that pre-compiles bytecode from .NET assemblies. This program is itself a .NET program - so far I've been able to use reflection to extract all the needed information including the bytecode itself. However, I've run into a problem implementing the translation for ldfld.

ldfld and similar instructions have a metadata token within their encoding which references a FieldRef or FieldDef. I understand these are elements in metadata tables embedded in the assembly's PE file. In the worst-case I do have enough information from ECMA-335 to open the PE file and look all this up myself, but that's a lot of work and is not consistent with other information which I do get through Reflection, so I would prefer to do this lookup via Reflection.

However, I can't seem to find any methods on System.Reflection.Assembly that look up a metadata token. (I may have just missed it.) I can't do the lookup on anything more specific than an assembly because I only know the referencing assembly until I see the metadata (catch-22.) In fact, as noted in the comments, I don't even know what assembly the field is defined in, until examining the metadata.

Is there any way to look up such metadata tokens via Reflection?

Answer 1

You didn't find anything on Assembly, because FieldDef and FieldRef don't belong to an assembly, they belong to a module (most assemblies have just a single module, but they can have more). And Module has exactly the method you want: ResolveField(). You would use it something like this:

Module module = …;
int fieldToken = …;
FieldInfo field = module.ResolveField(fieldToken);