>>>>I don't think there should be a performance issue. Given:

>>>>   public static class MyExtensions
>>>>    {
>>>>        public static string AddOn(this string s, string s1)
>>>>        {
>>>>            return s + s1;
>>>>        }
>>>>    }

then

string str = "Hello".AddOn(" Fred");

is just syntatic sugar for

string str = MyExtensions.AddOn("Hello", " Fred");

i.e. as far as the compiler is concerned they are identical
>>>
>>>
>>>
>>>Actually, I didn't see how there could be any performance issues either ... the guy who told me this though is usually pretty astute about such things, which is why I wondered about it. Could be that he was wrong. ;-)
>>>
>>
>>Well, he is a man ;-)
>
>As in, "If a man speaks and there isn't a woman to hear him is he still wrong?" :)

The way I heard it was "in the forest" -- play on "If a tree falls in the forest and there is no one there to hear it, is there still sound?"

(To which my answer is yes, right?)