As a general practice it's bad to return List<T> for that reason - it's bloated with additional members and state to match to support just-about-anything out of

As a general practice it's bad to return List<T> for that reason - it's bloated with additional members and state to match to support just-about-anything out of the box. Return IList instead of List on any public interface you define is the rule I try to obey. Basically it's all about how you implement arrays in your called classes - do they expose some internal state by returning a deep clone of the array each time it's called (which is what the examples Eric used were doing) or does it expose its contents via a read-only List?