Given a base class with the following interface:
public class Base
{
public virtual IEnumerable GetListOfStuff()
{
yield return \"F
Incidentally, the reason for this odd behaviour is that the CLR security team changed the verifier right before v2 shipped, such that it became unverifiable to do a non-virtual call on a virtual method of one class from a method in a different class.
For further explanation of this issue see my article on the subject from a few years back.
http://blogs.msdn.com/ericlippert/archive/2005/11/14/why-are-base-class-calls-from-anonymous-delegates-nonverifiable.aspx
This is now out-of-date; we've fixed up the compiler so that it now generates the helper for you.