A method group is the name for a set of methods (that might be just one) – i.e. in theory the ToString
method may have multiple overloads (plus any extension methods): ToString()
, ToString(string format)
, etc – hence ToString
by itself is a “method group”.
It can usually convert a method group to a (typed) delegate by using overload resolution – but not to a string etc; it doesn’t make sense.
Once you add parentheses, again; overload resolution kicks in and you have unambiguously identified a method call.