I found another oddity today, although if I think about it it's rather more of a cruel irony . The MSDN docs for Activator.CreateInstance(Ap... domain, string assemblyName, string typeName) state that if you pass in a null value for the "assemblyName" then the current assembly is searched. Unfortunetely, upon calling it I found that a System.NullReference exception is thrown instead. And now the cruel irony: Activator.CreateInstance(Ap... someDomain...) indeed doesn't check for the "assemblyName"...