How to determine if DLL is debug or release?

Howdy all,

Is there an easy way to tell if a DLL has been compiled in DEBUG or RELEASE mode?  I know I can put special checks in the code myself that would show up in a decompiler like Reflector, but if I have a set of DLLs that have already been deployed to a customer by other developers, can I examine those DLLs somehow to make sure they were compiled in RELEASE mode?

Thanks,
Dan