ToList does not shortcut if input is already a list
c#, linq
Solution
A read only collection can't be modified so it is perfectly acceptable to return the same instance as a result of `.ToReadOnlyCollection()`.
If the result of a `.ToList()` operation sometimes returned a new list and sometimes didn't you wouldn't know if you're modifying the source list when changing the output list. So, for this reason, `.ToList()` always returns a new instance.
Problem
The ToReadOnlyCollection extension method is implemented with a shortcut statement to return the input directly if it is already an instance of ReadOnlyCollection. The ToList extension method isnt. Purely out of curiosity, is there a particular reason for this, or just something that happens not to have been implemented. I can see why guaranteeing that `ToList` will always return a new instance might be useful, but id be interested to know if theres any other reason.